{{Article summary text|Covers various aspects of the next generation of the GRand Unified Bootloader (GRUB2).}}

{{Article summary text|Covers various aspects of the next generation of the GRand Unified Bootloader (GRUB2).}}

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{{Article summary text|{{Boot process overview}}}}

{{Article summary text|{{Boot process overview}}}}

{{Article summary heading|Related}}

{{Article summary heading|Related}}

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{{Article summary wiki|Burg}} - Burg is a brand-new boot loader based on GRUB2. It uses a new object format which allows it to be built in a wider range of OS, including Linux/Windows/OSX/Solaris/FreeBSD, etc. It also has a highly configurable menu system which works in both text and graphic mode.

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{{Article summary wiki|BURG}} - BURG is a brand-new boot loader based on GRUB2. It can be built on a wider range of OS, and has a highly configurable menu system which works in both text and graphic mode.

[https://www.gnu.org/software/grub/ GRUB2] is the next generation of the GRand Unified Bootloader (GRUB). GRUB2 is derived from [http://www.nongnu.org/pupa/ PUPA] which was a research project to investigate the next generation of GRUB. GRUB2 has been rewritten from scratch to clean up everything and provide modularity and portability [https://www.gnu.org/software/grub/grub-faq.html#q1].

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[http://www.gnu.org/software/grub/ GRUB2] is the next generation of the GRand Unified Bootloader (GRUB). GRUB2 is derived from [http://www.nongnu.org/pupa/ PUPA] which was a research project to investigate the next generation of GRUB. GRUB 2 has been rewritten from scratch to clean up everything and provide modularity and portability [http://www.gnu.org/software/grub/grub-faq.en.html#q1].

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In brief, the ''bootloader'' is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the Linux kernel. The kernel, in turn, initializes the rest of the operating system.

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Briefly, the ''bootloader'' is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the Linux kernel. The kernel, in turn, initializes the rest of the operating system.

== Preface ==

== Preface ==

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Here is some information that needs to be clarified:

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* The name ''GRUB'' officially refers to version ''2'' of the software, see [https://www.gnu.org/software/grub/]. If you are looking for the article on the legacy version, see [[GRUB Legacy]].

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Although, [[GRUB]] (i.e. version 0.9x) is the de facto standard bootloader of Linux, it is considered 'legacy' by upstream. It is being replaced by GRUB2 in many distributions. Upstream recommends GRUB2 >=1.99~rc2 over grub-legacy, even for current grub-legacy users.

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* From 1.99-6 onwards, GRUB2 supports [[Btrfs]] as root (without a separate {{ic|/boot}} filesystem) compressed with either zlib or LZO.

* For GRUB2 UEFI info, it is recommended to read the [[Unified Extensible Firmware Interface|UEFI]], [[GUID Partition Table|GPT]] and [[UEFI Bootloaders]] pages before reading this page.

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=== Notes for current GRUB users ===

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=== Notes for current GRUB Legacy users ===

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* Upgrade from [[GRUB Legacy]] to GRUB2 is the much same as fresh installing GRUB2 which is covered [[#Installation|below]].

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* There are differences in the commands of GRUB and GRUB2. Familiarize yourself with [http://www.gnu.org/software/grub/manual/grub.html#Commands GRUB2 commands] before proceeding (e.g. "find" has been replaced with "search").

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* There are differences in the commands of GRUB and GRUB2. Familiarize yourself with [https://www.gnu.org/software/grub/manual/grub.html#Commands GRUB2 commands] before proceeding (e.g. "find" has been replaced with "search").

* GRUB2 is now ''modular'' and no longer requires "stage 1.5". As a result, the bootloader itself is limited -- modules are loaded from the hard drive as needed to expand functionality (e.g. for [[LVM]] or RAID support).

* GRUB2 is now ''modular'' and no longer requires "stage 1.5". As a result, the bootloader itself is limited -- modules are loaded from the hard drive as needed to expand functionality (e.g. for [[LVM]] or RAID support).

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* Device naming has changed between GRUB and GRUB2. Partitions are numbered from 1 instead of 0 while drives are still numbered from 0, and prefixed with partition-table type. For example, {{Filename|/dev/sda1}} would be referred to as {{Codeline|(hd0,msdos1)}} (for MBR) or {{Codeline|(hd0,gpt1)}} (for GPT) using GRUB2.

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* Device naming has changed between GRUB and GRUB2. Partitions are numbered from 1 instead of 0 while drives are still numbered from 0, and prefixed with partition-table type. For example, {{ic|/dev/sda1}} would be referred to as {{ic|(hd0,msdos1)}} (for MBR) or {{ic|(hd0,gpt1)}} (for GPT) using GRUB2.

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=== Preliminary Requirements for GRUB2 ===

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==== BIOS systems ====

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===== [[GUID Partition Table]] (GPT) specific instructions =====

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GRUB2 in BIOS-GPT configuration requires a [http://www.gnu.org/software/grub/manual/html_node/BIOS-installation.html BIOS Boot Partition] to embed its {{ic|core.img}} in the absence of post-MBR gap in GPT partitioned systems (which is taken over by the GPT Primary Header and Primary Partition table). This partition is used by GRUB2 only in BIOS-GPT setups. No such partition type exists in case of MBR partitioning (at least not for GRUB2). This partition is also not required if the system is UEFI based, as no embedding of bootsectors takes place in that case. Syslinux does not require this partition.

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For a BIOS-GPT configuration, create a 1007 KiB partition at the beginning of the disk using cgdisk or GNU Parted with no filesystem. The size of 1007 KiB will allow for the following partition to be correctly alligned at 1024 KiB. If needed, the partition can also be located somewhere else on the disk, but it should be within the first 2 TiB region. Set the partition type to {{ic|0xEF02}} in gdisk, {{ic|EF02}} in cgdisk or {{ic|set <BOOT_PART_NUM> bios_grub on}} in GNU Parted.

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{{Note|This partition should be created before {{ic|grub-install}} or {{ic|grub-setup}} is run.}}

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{{Note|gdisk will only allow you to create this partition on the position which will waste the least amount of space (sector 34-2047) if you create it last, after all the other partitions. This is because gdisk will auto-align partitions to 2048-sector boundaries if possible.}}

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===== [[Master Boot Record]] (MBR) specific instructions =====

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Usually the post-MBR gap (after the 512 byte MBR region and before the start of the 1st partition) in many MBR (or msdos disklabel) partitioned systems is 31 KiB when DOS compatibility cylinder alignment issues are satisfied in the partition table. However a post-MBR gap of about 1 to 2 MiB is recommended to provide sufficient room for embedding GRUB2's {{ic|core.img}} ({{bug|24103}}). It is advisable to use a partitioner which supports 1 MiB partition alignment to obtain this space as well as satisfy other non-512 byte sector issues (which are unrelated to embedding of {{ic|core.img}}).

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MBR partitioning has better support in other operating systems, such as Microsoft Windows (up to Windows 7) and Haiku, than GPT partitioning. If you dual boot another operating system, consider using MBR partitioning.

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A MBR disk may be convertible to GPT if there is a small amount of extra space available. See [[GUID Partition Table#Convert from MBR to GPT]]

Follow [[Unified Extensible Firmware Interface#EFI System Partition]] for instructions on creating a UEFI SYSTEM PARTITION. Then mount the UEFI SYSTEM PARTITION at {{ic|/boot/efi}}. If you have mounted the UEFISYS partition in some other mountpoint, replace {{ic|/boot/efi}} in the below instructions with that mountpoint:

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# mkdir -p /boot/efi

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# mount -t vfat <UEFISYS_PART_DEVICE> /boot/efi

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Create a <UEFI_SYSTEM_PARTITION>{{ic|/EFI}} directory, if it does not exist:

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# mkdir -p /boot/efi/EFI

== Installation ==

== Installation ==

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=== During Arch Linux installation ===

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=== BIOS systems ===

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==== Backup Important Data ====

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Although a GRUB(2) installation should run smoothly, it is strongly recommended to keep the GRUB Legacy files before installing {{Pkg|grub-bios}}.

Only 446 bytes of the MBR contain boot code, the next 64 contain the partition table. If you do not want to overwrite your partition table when restoring, it is strongly advised to backup only the MBR boot code:

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# dd if=/dev/sdX of=/path/to/backup/bootcode_backup bs=446 count=1

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If unable to install GRUB2 correctly, see [[#Restore GRUB Legacy]].

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==== Install grub-bios package ====

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The GRUB(2) packages can be installed with pacman (and will replace {{Pkg|grub-legacy}} or {{Pkg|grub}}, if it is installed):

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# pacman -S grub-bios

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{{Note|Simply installing the package won't update the {{ic|/boot/grub/i386-pc/core.img}} file and the GRUB(2) modules in {{ic|/boot/grub/i386-pc}}. You need to update them manually using {{ic|grub-install}} as explained below.}}

* If you did not configure the installed system's {{Filename|/etc/resolv.conf}} file during installation (for instance, if you plan to let DHCP generate it later), you will need to copy the one generated by AIF when it configured the network:

{{Note|This is necessary at this point, and cannot be postponed after the chroot. If you try to use modprobe in a chroot environment that has a later kernel version from that of the installing device (at the time of writing, 2.6.33), modprobe will fail. This happens routinely using the Arch "net" installations.}}

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# grub-install --recheck /dev/sda

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* From the installer's live shell, chroot to the installed system:

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# grub-mkconfig -o /boot/grub/grub.cfg

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# mount -o bind /dev /mnt/dev

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# chroot /mnt bash

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where {{ic|/dev/sda}} is the destination of the installation (in this case the MBR of the first SATA disk). If you use [[LVM]] for your {{ic|/boot}}, you can install GRUB2 on multiple physical disks.

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* Update pacman's database:

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# pacman-db-upgrade

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{{Note|{{ic|--no-floppy}} has been removed from {{ic|grub-install}} in 2.00~beta2 upstream release, and replaced with {{ic|--allow-floppy}}.}}

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* Refresh the package list (with an extra -y flag to force a refresh of all package lists even if they appear to be up to date):

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# pacman -Syy

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{{Warning|Make sure to check the {{ic|/boot}} directory if you use the latter. Sometimes the {{ic| boot-directory}} parameter creates another {{ic|/boot}} folder inside of {{ic|/boot}}. A wrong install would look like: {{ic|/boot/boot/grub/}}.}}

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* Install the GRUB2 package as mentioned in the section [[#From a running Arch Linux]]. Note that the dm-mod module has already been loaded, no need to do that again.

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===== Install to GPT BIOS Boot Partition =====

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=== From a running Arch Linux ===

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[[GUID Partition Table]] disks do not have a reserved "boot track". Therefore you must create a BIOS Boot Partition (0xEF02) to hold the GRUB core image.

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==== BIOS systems ====

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Using GNU Parted, you can set this using a command such as the following:

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# parted /dev/disk set <partition-number> bios_grub on

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The GRUB2 package can be installed with pacman (and will replace {{Package Official|grub}}, if it is installed):

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If you are using gdisk, set the partition type to {{Keypress|0xEF02}}. With partitioning programs that require setting the GUID directly, it should be {{ic|‘21686148-6449-6e6f-744e656564454649’}} (stored on disk as {{ic|"Hah!IdontNeedEFI"}} if interpreted as ASCII).

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# pacman -S grub2-bios

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{{Note|When installing the grub2-common 1.99~rc1 (or later), this took quite some time because the installer does not use the option <code>--no-floppy</code>, for more details search this option in the article.}}

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{{Warning|Be very careful which partition you select when marking it as a BIOS Boot Partition. When GRUB finds a BIOS Boot Partition during installation, it will automatically overwrite part of it. Make sure that the partition does not contain any other data.}}

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Then GRUB2 must be installed to the boot sector of a drive or partition:

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To setup {{ic|grub-bios}} on a GPT disk, populate the {{ic|/boot/grub}} directory, generate the {{ic|/boot/grub/i386-pc/core.img}} file, and embed it in the BIOS Boot Partition, run:

To generate a {{Filename|core.img}} file alone without setting up grub2 in the MBR, add <code>--grub-setup=/bin/true</code> to grub2_bios-install:

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===== Install to Partition or Partitionless Disk =====

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{{Note|{{ic|grub-bios}} (any version - including upstream Bazaar repo) does not encourage installation to a partition boot sector or a partitionless disk like GRUB Legacy or Syslinux does. This kind of setup is prone to breakage, especially during updates, and is not supported by Arch devs.}}

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To set up {{ic|grub-bios}} to a partition boot sector, to a partitionless disk (also called superfloppy) or to a floppy disk, run (using for example {{ic|/dev/sdaX}} as the {{ic|/boot}} partition):

You need to use the {{ic|--force}} option to allow usage of blocklists and should not use {{ic|1=--grub-setup=/bin/true}} (which is similar to simply generating {{ic|core.img}}).

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{{ic|grub-install}} will give out warnings like which should give you the idea of what might go wrong with this approach:

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/sbin/grub-setup: warn: Attempting to install GRUB to a partitionless disk or to a partition. This is a BAD idea.

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/sbin/grub-setup: warn: Embedding is not possible. GRUB can only be installed in this setup by using blocklists.

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However, blocklists are UNRELIABLE and their use is discouraged.

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You can then chainload grub2's core.img from grub-legacy as a Linux kernel or a multiboot kernel.

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Without {{ic|--force}} you may get the below error and {{ic|grub-setup}} will not setup its boot code in the partition boot sector:

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The {{Codeline|--no-floppy}} tells to not search for floppy devices which will vastly improve the command's overall execution time on many systems (it will also prevent the issue below from occuring) and where {{Filename|/dev/sda}} is the destination of the installation (in this case the MBR of the first SATA disk). If you use [[LVM]] for your {{Filename|/boot}}, you can install GRUB2 on multiple physical disks.

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/sbin/grub-setup: error: will not proceed with blocklists

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Executing grub_bios-install without the {{Codeline|--no-floppy}} flag can also lead to this when there is a problem detecting the path of the floppy device:

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With {{ic|--force}} you should get:

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grub-probe: error: Cannot get the real path of '/dev/fd0'

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Installation finished. No error reported.

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Auto-detection of a filesystem module failed.

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Please specify the module with the option '--modules' explicitly.

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Thus it is recommended to use the {{Codeline|--no-floppy}} switch, if you do not want to have your MBR on a floppy. If you do, you also want to set floppy as the first boot device in BIOS.

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The reason why {{ic|grub-setup}} does not by default allow this is because in case of partition or a partitionless disk is that {{ic|grub-bios}} relies on embedded blocklists in the partition bootsector to locate the {{ic|/boot/grub/i386-pc/core.img}} file and the prefix dir {{ic|/boot/grub}}. The sector locations of {{ic|core.img}} may change whenever the filesystem in the partition is being altered (files copied, deleted etc.). For more info see https://bugzilla.redhat.com/show_bug.cgi?id=728742 and https://bugzilla.redhat.com/show_bug.cgi?id=730915.

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Finally, generate a configuration for grub2 (this is explained in greater detail in the Configuration section):

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The workaround for this is to set the immutable flag on {{ic|/boot/grub/i386-pc/core.img}} (using chattr command as mentioned above) so that the sector locations of the {{ic|core.img}} file in the disk is not altered. The immutable flag on {{ic|/boot/grub/i386-pc/core.img}} needs to be set only if {{ic|grub-bios}} is installed to a partition boot sector or a partitionless disk, not in case of installation to MBR or simple generation of {{ic|core.img}} without embedding any bootsector (mentioned above).

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# grub-mkconfig -o /boot/grub/grub.cfg

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===== Generate core.img alone =====

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===== [[GPT]] specific instructions =====

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To populate the {{ic|/boot/grub}} directory and generate a {{ic|/boot/grub/i386-pc/core.img}} file '''without''' embedding any {{ic|grub-bios}} bootsector code in the MBR, post-MBR region, or the partition bootsector, add {{ic|1=--grub-setup=/bin/true}} to {{ic|grub-install}}:

GRUB2 in BIOS-GPT configuration requires a BIOS Boot Partition to embed its core.img in the absence of 32 KiB post MBR gap in GPT partitioned systems.

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You can then chainload GRUB2's {{ic|core.img}} from GRUB Legacy or syslinux as a Linux kernel or a multiboot kernel.

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Create a 1 MiB (minimum size) partition using gdisk or GNU Parted with no filesystem. The location of the partition in the partition table does not matter but it should be within the first 2 TiB region of the GPT disk. It is advisable to put it somewhere in the beginning of the disk before the /boot partition. Set the partition type to "EF02" in GPT fdisk or set "bios_grub" flag on in GNU Parted or GParted.

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==== Generate GRUB2 BIOS Config file ====

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This partition is used by GRUB2 only in BIOS-GPT setups. No such partition type exists in case of MBR partitioning (at least not for GRUB2). This partition is also not required if the system is UEFI based, as no embedding takes place in that case. Neither GRUB-legacy nor SYSLINUX require this partition.

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Finally, generate a configuration for GRUB2 (this is explained in greater detail in the Configuration section):

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Note: This partition should be created before grub_bios-install or grub-setup is run or before the '''Install Bootloader''' step of the Archlinux installer (if GRUB2 is selected as bootloader).

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# grub-mkconfig -o /boot/grub/grub.cfg

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===== [[MBR]] aka msdos partitioning specific instructions =====

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Usually the post-MBR gap (after the 512 byte MBR region and before the start of the 1st partition) in many MBR (or msdos disklabel) partitioned systems is 32 KiB when DOS compatibility cylinder alignment issues are satisfied in the partition table. However a post-MBR gap of about 1 MiB is recommended to provide sufficient room for embedding grub2's core.img ( https://bugs.archlinux.org/task/24103 ). It is advisable to use a partitioner which supports 1 MiB partition alignment to obtain this space as well as satisfy other non-512 byte sector issues (which are unrelated to embedding of core.img).

If you forgot to create a GRUB2 {{ic|/boot/grub/grub.cfg}} config file and simply rebooted into GRUB2 Command Shell, type:

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==== [[UEFI]] systems ====

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sh:grub> insmod legacycfg

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sh:grub> legacy_configfile ${prefix}/menu.lst

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'''''Note: Unless specified as EFI 1.x , EFI and UEFI terms are used interchangeably to denote UEFI 2.x firmware. Also unless stated explicitely, the instructions are general and not Mac specific. Some of them may not work or may be different in Macs. Apple's EFI implementation is neither a EFI 1.1 version nor UEFI 2.x version but includes features of both. This kind of firmware does not fall under any one UEFI version so it is not a standard EFI firmware.'''''

GRUB2 UEFI bootloader is available in Arch Linux only from version 1.99~rc1 . To install, first [https://wiki.archlinux.org/index.php/Unified_Extensible_Firmware_Interface#Detecting_UEFI_Firmware_Arch Detect which UEFI firmware arch] you have (either x86_64 or i386).

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{{Note|This option works only in BIOS systems, not in UEFI systems.}}

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==== Multiboot in BIOS ====

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===== Boot Microsoft Windows installed in BIOS-MBR mode =====

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{{Note|GRUB(2) supports booting {{ic|bootmgr}} directly and chainload of partition boot sector is no longer required to boot Windows in a BIOS-MBR setup.}}

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{{Warning|Take note that it is the '''system partition''' that has {{ic|bootmgr}}, not your "real" Windows partition (usually C:). When showing all UUIDs with blkid, the system partition is the one with {{ic|LABEL&#61;"SYSTEM RESERVED"}} and is only about 100 MB in size (much like the boot partition for Arch). See http://en.wikipedia.org/wiki/System_partition_and_boot_partition for more info.}}

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Find the UUID of the NTFS filesystem of the Windows's SYSTEM PARTITION where the {{ic|bootmgr}} and its files reside. For example, if Windows {{ic|bootmgr}} exists at {{ic|/media/SYSTEM_RESERVED/bootmgr}}:

{{ic|/etc/grub.d/40_custom}} can be used as a template to create {{ic|/etc/grub.d/nn_custom}}. Where nn defines the precendence, indicating the order the script is executed. The order scripts are executed determine the placement in the grub boot menu.

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{{Note| nn should be greater than 06 to ensure necessary scripts are executed first.}}

It is well know that different motherboard manufactures implement UEFI differently. Users experiencing problems getting Grub/EFI to work properly are encouraged to share detailed steps for hardware-specific cases where UEFI booting does not work as described below. In an effort to keep the parent [[GRUB]] article neat and tidy, see the [[GRUB EFI Examples]] page for these special cases.

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==== Install grub-uefi package ====

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{{Note|Unless specified as EFI 1.x , EFI and UEFI terms are used interchangeably to denote UEFI 2.x firmware. Also unless stated explicitly, the instructions are general and not Mac specific. Some of them may not work or may be different in Macs. Apple's EFI implementation is neither a EFI 1.x version nor UEFI 2.x version but mixes up both. This kind of firmware does not fall under any one UEFI Specification version and is therefore not a standard UEFI firmware.}}

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GRUB(2) UEFI bootloader is available in Arch Linux only from version 1.99~rc1. To install, first [[Unified Extensible Firmware Interface#Detecting UEFI Firmware Arch|detect which UEFI firmware arch]] you have (either x86_64 or i386).

Depending on that, install the appropriate package

Depending on that, install the appropriate package

For 64-bit aka x86_64 UEFI firmware:

For 64-bit aka x86_64 UEFI firmware:

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# pacman -S grub2-efi-x86_64

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# pacman -S grub-efi-x86_64

For 32-bit aka i386 UEFI firmware:

For 32-bit aka i386 UEFI firmware:

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# pacman -S grub2-efi-i386

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# pacman -S grub-efi-i386

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{{Note|Simply installing the package will not update the {{ic|core.efi}} file and the GRUB(2) modules in the UEFI System Partition. You need to do this manually using {{ic|grub-install}} as explained below.}}

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==== Install grub-uefi boot files ====

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===== Install to UEFI System Partition =====

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{{Note|The below commands assume you are using {{ic|grub-efi-x86_64}} (for {{ic|grub-efi-i386}} replace {{ic|x86_64}} with {{ic|i386}} in the below commands).}}

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{{Note|To do this, you need to boot using UEFI and not the BIOS. If you booted by just copying the ISO file to the USB drive, you will need to follow [[Unified Extensible Firmware Interface#Create UEFI bootable USB from ISO|this guide]] or grub-install will show errors.}}

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The UEFI system partition will need to be mounted at {{ic|/boot/efi/}} for the GRUB(2) install script to detect it:

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# mkdir -p /boot/efi

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# mount -t vfat /dev/sdXY /boot/efi

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Install GRUB UEFI application to {{ic|/boot/efi/EFI/arch_grub}} and its modules to {{ic|/boot/grub/x86_64-efi}} (recommended) using:

{{Note|Without {{ic|--target}} or {{ic|--directory}} option, grub-install cannot determine for which firmware grub(2) is being installed. In such cases grub-install will show {{ic|source_dir doesn't exist. Please specify --target or --directory}} message.}}

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If you want to install grub(2) modules and {{ic|grub.cfg}} at the directory {{ic|/boot/efi/EFI/grub}} and the {{ic|grubx64.efi}} application at {{ic|/boot/efi/EFI/arch_grub}} (ie. all the grub(2) uefi files inside the UEFISYS partition itself) use:

The {{ic|--efi-directory}} option mentions the mountpoint of UEFI SYSTEM PARTITION , {{ic|--bootloader-id}} mentions the name of the directory used to store the {{ic|grubx64.efi}} file and {{ic|--boot-directory}} mentions the directory wherein the actual modules will be installed (and into which {{ic|grub.cfg}} should be created).

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The actual paths are:

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Mount the [https://wiki.archlinux.org/index.php/Unified_Extensible_Firmware_Interface#Creating_a_EFI_SYSTEM_PARTITION_in_Linux EFI SYSTEM PARTITION] in your system at {{Filename|/boot/efi}}. It should be FAT32 formatted and should be at least 200 MB in size. If you have mounted the EFISYS partition in some other mountpoint, replace {{Filename|/boot/efi}} in the below commands with that mountpoint:

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<efi-directory>/<EFI or efi>/<bootloader-id>/grubx64.efi

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# sudo mkdir -p /boot/efi/efi # If the directory does not exist

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# sudo modprobe dm-mod

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The below commands assume you are using {{Codeline|grub2-efi-x86_64}} (for {{Codeline|grub2-efi-i386}}, replace {{Codeline|x86_64}} with {{Codeline|i386}} in the below commands):

If you notice carefully, there is no <device_path> option (Eg: {{Filename|/dev/sda}}) at the end of the {{Codeline|grub_efi_x86_64-install}} command unlike the case of setting up grub2 for BIOS systems. Any <device_path> provided will be ignored by the install script as UEFI bootloaders do not use MBR or Partition boot sectors at all.

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{{Note|the {{ic|--bootloader-id}} option does not change {{ic|<boot-directory>/grub}}, i.e. you cannot install the modules to {{ic|<boot-directory>/<bootloader-id>}}, the path is hard-coded to be {{ic|<boot-directory>/grub}}.}}

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Then copy the font files required to enable UEFI video mode (GOP mostly) in grub2 (otherwise no kernel boot messages will be seen in the console):

A "{{Filename|grub.cfg}}" created for BIOS based GRUB2 will be sufficient for the UEFI GRUB2 as long as all the paths in the config are absolute paths. The {{Filename|grub.efi}} UEFI application can be launched using the firmware's "Boot Manager", "Boot from file" option or using the [https://wiki.archlinux.org/index.php/UEFI#UEFI_Shell UEFI Shell].

Alternatively, you can also setup {{Filename|/boot/efi/efi/grub}} directory by copying all the files in {{Filename|/usr/lib/grub/x86_64-efi}} to {{Filename|/boot/efi/efi/grub}} and using the above grub-mkimage command to create a {{Filename|grub2.efi}} application. Just make sure you have the required modules embedded in {{Filename|grub2.efi}} to enable it to access the EFI SYSTEM PARTITION.

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<efi-directory>/<EFI or efi>/<bootloader-id> == /boot/efi/EFI/grub

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<boot-directory>/grub == /boot/grub

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A basic {{Filename|grub2.efi}} can be generated using the following command:

+

The {{ic|<nowiki><efi-directory>/<EFI or efi>/<bootloader-id>/grubx64.efi</nowiki>}} is an exact copy of {{ic|<nowiki><boot-directory>/grub/x86_64-efi/core.efi</nowiki>}}.

In the {{Filename|/boot/efi/efi/grub/grub.cfg}} file, add the following lines to enable grub2 to pass the video mode correctly to the kernel, without of which you will only get a black screen (no output) but booting (actually) proceeds successfully without any system hang:

+

{{Note|The options {{ic|--efi-directory}} and {{ic|--bootloader-id}} are specific to GRUB(2) UEFI.}}

−

<pre>

+

−

insmod efi_gop

+

In all the cases the UEFI SYSTEM PARTITION should be mounted for {{ic|grub-install}} to install {{ic|grubx64.efi}} in it, which will be launched by the firmware (using the {{ic|efibootmgr}} created boot entry in non-Mac systems).

−

insmod efi_uga

+

−

insmod font

+

If you notice carefully, there is no <device_path> option (Eg: {{ic|/dev/sda}}) at the end of the {{ic|grub-install}} command unlike the case of setting up GRUB(2) for BIOS systems. Any <device_path> provided will be ignored by the install script as UEFI bootloaders do not use MBR or Partition boot sectors at all.

−

if loadfont ${prefix}/unicode.pf2

+

You may now be able to UEFI boot your system by creating a {{ic|grub.cfg}} file by following [[#Generate GRUB2 UEFI Config file]] and [[#Create GRUB2 entry in the Firmware Boot Manager]].

−

then

−

insmod gfxterm

−

set gfxmode=auto

−

set gfxpayload=keep

−

terminal_output gfxterm

−

fi

−

</pre>

−

As you can see for gfxterm (graphical terminal) to function properly, {{Filename|unicode.pf2}} font file should exist in {{Filename|/boot/efi/efi/grub/}}.

+

==== Generate GRUB2 UEFI Config file ====

−

===== Launch GRUB2 as default in (U)EFI Boot Manager =====

+

Finally, generate a configuration for GRUB(2) (this is explained in greater detail in the Configuration section):

−

====== For non-Mac UEFI systems ======

+

# grub-mkconfig -o <boot-directory>/grub/grub.cfg

−

'''NOTE: The below steps will not work if the system has been booted in BIOS mode and will not work if the UEFI processor architecture does not match the kernel one, i.e. x86_64 UEFI + ix86 32-bit Kernel and vice-versa config will not work.'''

grub_efi_${UEFI_ARCH}-install will ensure {{Filename|/boot/efi/efi/grub/grub.efi}} is launched by default if it detects {{Codeline|efibootmgr}} and if it is able to access UEFI Runtime Services. {{Codeline|efibootmgr}} command will work only if you have booted the system in UEFI mode itself, since it '''requires access to UEFI Runtime Variables''' which are '''available only in UEFI boot mode''' (with "noefi" kernel parameter NOT being used). Initially the user is required to manually launch {{Filename|/boot/efi/efi/grub/grub.efi}} from the firmware itself (using maybe the UEFI Shell) if grub2-efi was installed in BIOS mode. Then {{Codeline|efibootmgr}} should be run to make grub2 as the default entry in the UEFI Boot Manager

+

If you used {{ic|<nowiki>--boot-directory=/boot</nowiki>}}:

−

First boot into UEFI mode manually either using the firmware boot menu, UEFI shell, or using any UEFI capable bootable iso (Archboot or Ubuntu non-Mac iso). Use grub probe to determine the device path of your EFI System Partition:

+

# grub-mkconfig -o /boot/grub/grub.cfg

−

# grub-probe --target=device /boot/efi/efi/grub/grub.efi

−

It should give something like {{Filename|/dev/sda1}} (used as example in the remaining steps). Load 'efivars' kernel module:

+

If you used {{ic|<nowiki>--boot-directory=/boot/efi/EFI</nowiki>}}:

−

# sudo modprobe efivars

−

If you get '''no such device found''' error for this command, that means you have not booted in UEFI mode and due to some reason the kernel is unable to access UEFI Runtime Variables.

+

# grub-mkconfig -o /boot/efi/EFI/grub/grub.cfg

−

Verify whether there are files in ''/sys/firmware/efi/vars/'' directory. This directory and its contents are created by "efivars" kernel module and it will exist only if you have booted in UEFI mode without "noefi" parameter.

If ''/sys/firmware/efi/vars/'' directory is empty or does not exist, then {{Codeline|efibootmgr}} command will not work. If you are unable to make the ISO/CD/DVD/USB boot in UEFI mode try https://gitorious.org/tianocore_uefi_duet_builds/pages/Linux_Windows_BIOS_UEFI_boot_USB .

+

==== Create GRUB2 entry in the Firmware Boot Manager ====

−

If ''/sys/firmware/efi/vars/'' directory (along with the exists then run {{Codeline|efibootmgr}} and reboot:

+

As of grub-efi-x86_64 version 2.00, {{ic|grub-install}} automatically tries to create a menu entry in the boot manager. If it doesn't, then see [[Beginners' Guide#GRUB]] for instructions to use {{ic|efibootmgr}} to create a menu entry. However, the problem is likely to be that you haven't booted your CD/USB in UEFI mode, as in [[Unified Extensible Firmware Interface#Create UEFI bootable USB from ISO]].

In the above command, {{Filename|/boot/efi/efi/grub/grub/efi}} can be split up as {{Filename|/boot/efi}} and {{Filename|/efi/grub/grub.efi}}, which translates to {{Filename|(/dev/sda)}} -> partition 1 -> {{Filename|\\EFI\\grub\\grub.efi}}.

+

==== Create GRUB2 Standalone UEFI Application ====

−

Note the capital EFI, FAT32 fs is case-insensitive since it does not use UTF-8 encoding by default. In that case the firmware uses capital 'EFI' instead of small 'efi', although using {{Filename|\\EFI\\grub\\grub.efi}} should be just fine (this will change if the fs encoding is UTF-8). Also the path names in UEFI firmware are similar to Windows path names and also uses double backward slashes instead of single ones. The double backward slashes so that the first backward slash escapes the second one.

+

It is possible to create a {{ic|grubx64_standalone.efi}} application which has all the modules embeddded in a memdisk within the uefi application, thus removing the need for having a separate directory populated with all the GRUB2 uefi modules and other related files. This is done using the {{ic|grub-mkstandalone}} command which is included in {{Pkg|grub-common}} >= 1:1.99-6 package.

−

The 'label' is any name for just your identification and is the name of the menu entry shown in UEFI boot menu. It does not affect the booting of the system. More info can be obtained from [http://linux.dell.com/cgi-bin/gitweb/gitweb.cgi?p=efibootmgr.git;a=blob_plain;f=README;hb=HEAD efibootmgr GIT README]

+

The easiest way to do this would be with the install command already mentioned before, but specifying the modules to include. For example:

The {{ic|grubx64_standalone.efi}} file expects {{ic|grub.cfg}} to be within its $prefix which is {{ic|(memdisk)/boot/grub}}. The memdisk is embedded within the efi app. The {{ic|grub-mkstandlone}} script allow passing files to be included in the memdisk image to be as the arguments to the script (in <any extra files you want to include>).

−

{{Expansion}}

+

If you have the {{ic|grub.cfg}} at {{ic|/home/user/Desktop/grub.cfg}}, then create a temporary {{ic|/home/user/Desktop/boot/grub/}} directory, copy the {{ic|/home/user/Desktop/grub.cfg}} to {{ic|/home/user/Desktop/boot/grub/grub.cfg}}, cd into {{ic|/home/user/Desktop/boot/grub/}} and run:

The reason to cd into {{ic|/home/user/Desktop/boot/grub/}} and to pass the file path as {{ic|boot/grub/grub.cfg}} (notice the lack of a leading slash - boot/ vs /boot/ ) is because {{ic|dir1/dir2/file}} is included as {{ic|(memdisk)/dir1/dir2/file}} by the {{ic|grub-mkstandalone}} script.

−

GRUB2 for BIOS systems should be compiled as follows:

+

If you pass {{ic|/home/user/Desktop/grub.cfg}} the file will be included as {{ic|(memdisk)/home/user/Desktop/grub.cfg}}. If you pass {{ic|/home/user/Desktop/boot/grub/grub.cfg}} the file will be included as {{ic|(memdisk)/home/user/Desktop/boot/grub/grub.cfg}}. That is the reason for cd'ing into {{ic|/home/user/Desktop/boot/grub/}} and passing {{ic|boot/grub/grub.cfg}}, to include the file as {{ic|(memdisk)/boot/grub/grub.cfg}}, which is what {{ic|grub.efi}} expects the file to be.

−

<pre>

−

./autogen.sh

−

./configure --with-platform=pc --prefix=/usr

+

You need to create an UEFI Boot Manager entry for {{ic|/boot/efi/EFI/arch_grub/grubx64_standalone.efi}} using {{ic|efibootmgr}}. Follow [[#Create GRUB2 entry in the Firmware Boot Manager]].

−

make

+

==== Multiboot in UEFI ====

−

make install

+

===== Chainload Microsoft Windows x86_64 UEFI-GPT =====

−

</pre>

−

The <code>--with-platform=pc</code> generates grub2 for bios alone irrespective of the firmware of the build system.

+

Find the UUID of the FAT32 filesystem in the UEFI SYSTEM PARTITION where the Windows UEFI Bootloader files reside. For example, if Windows {{ic|bootmgfw.efi}} exists at {{ic|/boot/efi/EFI/Microsoft/Boot/bootmgfw.efi}} (ignore the upper-lower case differences since that is immaterial in FAT filesystem):

The "--target" option denotes the UEFI firmware arch. for which grub2 should be compiled, not the architecture of the linux kernel grub2 may boot.

+

Afterwards remake {{ic|/boot/grub/grub.cfg}}

−

It is possible to use UEFI 64-bit firmware + GRUB2 as x86_64-EFI app loading a i686 linux kernel, as long as the kernel does not try to access UEFI Runtime Services. Vice-versa situation is also possible. But a x86_64 UEFI firmware cannot launch GRUB2 i386-efi app (unlike x86_64 Operating Systems), and a i386 UEFI firmware will not launch GRUB2 {{Codeline|x86_64-efi}} app. It is important to compile GRUB2 to match the architecture of the UEFI firmware.

+

# grub-mkconfig -o /boot/grub/grub.cfg

== Configuration ==

== Configuration ==

−

The configuration files are {{Filename|/etc/default/grub}} and {{Filename|/etc/grub.d/*}}. These files are used to generate the {{Filename|/boot/grub/grub.cfg}} file. You can also choose to manually edit {{Filename|grub.cfg}}.

+

You can also choose to automatically generate or manually edit {{ic|grub.cfg}}.

+

+

{{Note|For EFI systems, if GRUB2 was installed with the {{ic|--boot-directory}} option set, the {{ic|grub.cfg}} file must be placed in the same directory as {{ic|grubx64.efi}}. Otherwise, the {{ic|grub.cfg}} file goes in {{ic|/boot/grub/}}, just like in the BIOS version of GRUB2.}}

+

+

{{Note|Here is a quite complete description of how to configure GRUB2: http://members.iinet.net/~herman546/p20/GRUB2%20Configuration%20File%20Commands.html }}

−

=== grub-mkconfig ===

+

=== Automatically generating using grub-mkconfig (Recommended) ===

+

+

The GRUB2 {{ic|menu.lst}} equivalent configuration files are {{ic|/etc/default/grub}} and {{ic|/etc/grub.d/*}}. {{ic|grub-mkconfig}} uses these files to generate {{ic|grub.cfg}}. By default the script outputs to stdout. To generate a {{ic|grub.cfg}} file run the command:

−

The grub-mkconfig script can be used to generate a {{Filename|grub.cfg}} file. By default the script outputs to stdout. Note that gettext ― an optional dependency of the GRUB2 package ― is required by the grub-mkconfig script. To generate a {{Filename|grub.cfg}} file run the command:

# grub-mkconfig -o /boot/grub/grub.cfg

# grub-mkconfig -o /boot/grub/grub.cfg

−

=== grub.cfg ===

+

{{ic|/etc/grub.d/10_linux}} is set to automatically add menu items for Arch linux that work out of the box, to any generated configuration. Other operating systems may need to be added manually to {{ic|/etc/grub.d/40_custom}} or {{ic|/boot/grub/custom.cfg}}

+

+

==== Additional arguments ====

+

+

To pass custom additional arguments to the Linux image, you can set the {{ic|GRUB_CMDLINE_LINUX}} variable in {{ic|/etc/default/grub}}.

+

+

For example, use {{ic|<nowiki>GRUB_CMDLINE_LINUX="resume=/dev/sdaX"</nowiki>}} where {{ic|sda'''X'''}} is your swap partition to enable resume after hibernation.

+

+

You can also use {{ic|<nowiki>GRUB_CMDLINE_LINUX="resume=/dev/disk/by-uuid/${swap_uuid}"</nowiki>}}, where {{ic|${swap_uuid} }} is the [[Persistent_block_device_naming|UUID]] of your swap partition.

+

+

Multiple entries are separated by spaces within the double quotes. So, for users who want both resume and systemd it would look like this:

{{Warning|Editing this file is strongly ''not'' recommended. The file is generated by the {{ic|grub-mkconfig}} command, and it is best to edit your {{ic|/etc/default/grub}} or one of the scripts in the {{ic|/etc/grub.d}} folder.}}

* {{Codeline|1=set root=(hdX,Y)}} sets the boot partition, where the kernel and GRUB modules are stored (boot need not be a separate partition, and may simply be a directory under the "root" partition ({{Filename|/}})

+

* {{ic|1=set root=(hdX,Y)}} sets the boot partition, where the kernel and GRUB modules are stored (boot need not be a separate partition, and may simply be a directory under the "root" partition ({{ic|/}})

An example configuration:

An example configuration:

−

{{File

+

{{hc

−

|name=/boot/grub/grub.cfg

+

|/boot/grub/grub.cfg

−

|content=<nowiki>

+

|<nowiki>

# Config file for GRUB2 - The GNU GRand Unified Bootloader

# Config file for GRUB2 - The GNU GRand Unified Bootloader

# /boot/grub/grub.cfg

# /boot/grub/grub.cfg

Line 348:

Line 535:

# (0) Arch Linux

# (0) Arch Linux

menuentry "Arch Linux" {

menuentry "Arch Linux" {

−

set root=(hd0,1)

+

set root=(hd0,1)

−

linux /vmlinuz-linux root=/dev/sda3 ro

+

linux /vmlinuz-linux root=/dev/sda3 ro

−

initrd /initramfs-linux.img

+

initrd /initramfs-linux.img

}

}

Line 362:

Line 549:

=== Dual-booting ===

=== Dual-booting ===

−

''NOTE: If you want GRUB2 to automatically search for other systems, for example as in Ubuntu. Then you may need to download {{Package AUR|os-prober}} from the [[AUR]].''

+

{{Note|If you want GRUB2 to automatically search for other systems, you may wish to install {{Pkg|os-prober}}.}}

==== Using grub-mkconfig ====

==== Using grub-mkconfig ====

−

The best way to add other entries is editing the {{Filename|/etc/grub.d/40_custom}}. The entries in this file will be automatically added when running '''grub-mkconfig'''.

+

The best way to add other entries is editing the {{ic|/etc/grub.d/40_custom}} or {{ic|/boot/grub/custom.cfg}} . The entries in this file will be automatically added when running {{ic|grub-mkconfig}}.

After adding the new lines, run:

After adding the new lines, run:

# grub-mkconfig -o /boot/grub/grub.cfg

# grub-mkconfig -o /boot/grub/grub.cfg

−

to generate an updated {{Filename|grub.cfg}}.

+

to generate an updated {{ic|grub.cfg}}.

===== With GNU/Linux =====

===== With GNU/Linux =====

−

Assuming that the other distro is on partition {{Filename|sda2}}:

+

Assuming that the other distro is on partition {{ic|sda2}}:

menuentry "Other Linux" {

menuentry "Other Linux" {

Line 378:

Line 565:

linux /boot/vmlinuz (add other options here as required)

linux /boot/vmlinuz (add other options here as required)

initrd /boot/initrd.img (if the other kernel uses/needs one)

initrd /boot/initrd.img (if the other kernel uses/needs one)

+

}

+

+

===== With FreeBSD =====

+

+

Requires that FreeBSD is installed on a single partition with UFS. Assuming it is installed on {{ic|sda4}}:

+

+

menuentry "FreeBSD" {

+

set root=(hd0,4)

+

chainloader +1

}

}

===== With Windows =====

===== With Windows =====

−

This assumes that your Windows partition is {{Filename|sda3}}.

+

This assumes that your Windows partition is {{ic|sda3}}. Remember you need to point set root and chainloader to the system reserve partition that windows made when it installed, not the actual partition windows is on. This example works if your system reserve partition is {{ic|sda3}}.

# (2) Windows XP

# (2) Windows XP

Line 390:

Line 586:

}

}

−

If the windows bootloader is on an entirely different harddrive than grub, it may be necessary to trick Windows into believing that it is in fact the first harddrive. This was possible in the old grub with {{Codeline|map}} and is now done with {{Codeline|drivemap}}. Assume grub is on {{Filename|hd0}} and windows on {{Filename|hd2}}, you need to add the following after {{Codeline|set root}}:

+

If the Windows bootloader is on an entirely different hard drive than GRUB, it may be necessary to trick Windows into believing that it is the first hard drive. This was possible with {{ic|drivemap}}. Assuming GRUB is on {{ic|hd0}} and Windows is on {{ic|hd2}}, you need to add the following after {{ic|set root}}:

drivemap -s hd0 hd2

drivemap -s hd0 hd2

Line 396:

Line 592:

==== With Windows via EasyBCD and NeoGRUB ====

==== With Windows via EasyBCD and NeoGRUB ====

−

Since EasyBCD's NeoGRUB currently does not understand the GRUB2 menu format, chainload to it by replacing the contents of your {{Filename|C:\NST\menu.lst}} file with lines similar to the following:

+

Since EasyBCD's NeoGRUB currently does not understand the GRUB2 menu format, chainload to it by replacing the contents of your {{ic|C:\NST\menu.lst}} file with lines similar to the following:

default 0

default 0

Line 403:

Line 599:

title Chainload into GRUB v2

title Chainload into GRUB v2

root (hd0,7)

root (hd0,7)

−

kernel /boot/grub/core.img

+

kernel /boot/grub/i386-pc/core.img

===Visual Configuration===

===Visual Configuration===

−

In GRUB2 it is possible, by default, to change the look of the menu.

+

In GRUB2 it is possible, by default, to change the look of the menu. Make sure to initialize, if not done already, GRUB2 graphical terminal, gfxterm, with proper video mode, gfxmode, in GRUB2. This can be seen in the section [[#Correct_GRUB2_No_Suitable_Mode_Found_Error]]. This video mode is passed by GRUB2 to the linux kernel via 'gfxpayload' so any visual configurations need this mode in order to be in effect.

−

====Background image and bitmap fonts====

+

====Setting the framebuffer resolution ====

−

GRUB2 comes with support for background images and bitmap fonts in pf2 format. The unifont font is included in the grub2 package under the filename {{Filename|unicode.pf2}}, or, as only ascii characters under the name {{Filename|ascii.pf2}}. Image formats supported include tga, png and jpeg, providing the correct modules are loaded. The maximum supported resolution depends on your hardware. There are two ways of setting a {{Filename|tga}} file as background. Two sample configurations are shown below.

+

GRUB2 can set the framebuffer for both GRUB2 itself and the kernel. The old {{ic|1=vga=}} way is deprecated. The preferred method is editing {{ic|/etc/default/grub}} as the following sample:

−

Edit {{Filename|/etc/default/grub}} like this:

GRUB_GFXMODE=1024x768x32

GRUB_GFXMODE=1024x768x32

GRUB_GFXPAYLOAD_LINUX=keep

GRUB_GFXPAYLOAD_LINUX=keep

−

GRUB_BACKGROUND="/boot/grub/archlinux.tga"

+

+

To generate the changes, run:

+

# grub-mkconfig -o /boot/grub/grub.cfg

+

+

The {{ic|gfxpayload}} property will make sure the kernel keeps the resolution.

+

+

{{Note|If this example does not work for you try to replace {{ic|1=gfxmode="1024x768x32"}} by {{ic|1=vbemode="0x105"}}. Remember to replace the specified resolution with one suitable for your screen.}}

+

{{Note|To show all the modes you can use {{ic|1=# hwinfo --framebuffer}} (hwinfo is available in [community]), while at GRUB2 prompt you can use the {{ic|1=vbeinfo}} command.}}

+

+

If this method does not work for you, the deprecated {{ic|1=vga=}} method will still work. Just

+

add it next to the {{ic|1="GRUB_CMDLINE_LINUX_DEFAULT="}} line in {{ic|/etc/default/grub}}

+

for eg: {{ic|1="GRUB_CMDLINE_LINUX_DEFAULT="quiet splash vga=792"}} will give you a {{ic|1024x768}} resolution.

+

+

You can choose one of these resolutions: {{ic|640×480}}, {{ic|800×600}}, {{ic|1024×768}}, {{ic|1280×1024}}, {{ic|1600×1200}}, {{ic|1920×1200}}

+

+

====915resolution hack ====

+

+

Some times for Intel graphic adapters neither {{ic|1=# hwinfo --framebuffer}} nor {{ic|1=vbeinfo}} will show you the desired resolution. In this case you can use {{ic|915resolution}} hack. This hack will temporarily modify video BIOS and add needed resolution. See [http://915resolution.mango-lang.org/ 915resolution's home page]

+

+

In the following I will proceed with the example for my system. Please adjust the recipe for your needs. First you need to find a video mode which will be modified later. For that, run {{ic|915resolution}} in GRUB2 command shell:

+

915resolution -l

+

The output will be something like:

+

Intel 800/900 Series VBIOS Hack : version 0.5.3

+

...

+

Mode 30 : 640x480, 8 bits/pixel

+

...

+

Next, our purpose is to overwrite mode 30. (You can choose what ever mode you want.) In the file {{ic|/etc/grub.d/00_header}} just before the {{ic|set gfxmode&#61;${GRUB_GFXMODE}}} line insert:

+

915resolution 30 1440 900

+

Here we are overwriting the mode {{ic|30}} with {{ic|1440x900}} resolution. Lastly we need to set {{ic|GRUB_GFXMODE}} as described earlier, regenerate GRUB2 configuration file and reboot to test changes:

+

# grub-mkconfig -o /boot/grub/grub.cfg

+

# reboot

+

+

====Background image and bitmap fonts====

+

+

GRUB2 comes with support for background images and bitmap fonts in {{ic|pf2}} format. The unifont font is included in the {{Pkg|grub-common}} package under the filename {{ic|unicode.pf2}}, or, as only ASCII characters under the name {{ic|ascii.pf2}}.

Make sure you have set up the proper [[#Setting the framebuffer resolution|framebuffer resolution]].

+

+

Edit {{ic|/etc/default/grub}} like this:

+

GRUB_BACKGROUND="/boot/grub/myimage"

#GRUB_THEME="/path/to/gfxtheme"

#GRUB_THEME="/path/to/gfxtheme"

+

GRUB_FONT="/path/to/font.pf2"

−

To generate the changes, run:

+

{{Note|If you have installed GRUB on a separate partition, {{ic|/boot/grub/myimage}} becomes {{ic|/grub/myimage}}.}}

+

+

To generate the changes and add the information into {{ic|grub.cfg}}, run:

+

grub-mkconfig -o /boot/grub/grub.cfg

+

+

If adding the splash image was successful, the user will see {{ic|"Found background image..."}} in the terminal as the command is executed.

+

If this phrase is not seen, the image information was probably not incorporated into the {{ic|grub.cfg}} file.

+

+

If the image is not displayed, check:

+

* The path and the filename in {{ic|/etc/default/grub}} are correct.

+

* The image is of the proper size and format (tga, png, 8-bit jpg).

+

* The image was saved in the RGB mode, and is not indexed.

+

* The console mode is not enabled in {{ic|/etc/default/grub}}.

+

* The command {{ic|grub-mkconfig}} must be executed to place the background image information into the {{ic|/boot/grub/grub.cfg}} file.

+

+

====Theme====

+

+

Here is an example for configuring Starfield theme which was included in GRUB2 package.

+

+

Edit {{ic|/etc/default/grub}}

+

GRUB_THEME="/usr/share/grub/themes/starfield/theme.txt"

+

+

Generate the changes:

grub-mkconfig -o /boot/grub/grub.cfg

grub-mkconfig -o /boot/grub/grub.cfg

−

{{Note|If this example does not work for you try to replace {{Codeline|1=gfxmode="1024x768x32"}} by {{Codeline|1=vbemode="0x105"}}.}}

+

If configuring the theme was successful, you'll see {{ic|Found theme: /usr/share/grub/themes/starfield/theme.txt}} in the terminal.

−

{{Note|To show all the modes you can use {{Codeline|1=# hwinfo --framebuffer}} (hwinfo is available in [community]), while at grub2 prompt you can use the {{Codeline|1=vbeinfo}} command.}}

+

Your splash image will usually not be displayed when using a theme.

−

{{Note|If you have installed Grub on a separate partition, {{Filename|/boot/grub/archlinux.tga}} becomes {{Filename|/grub/archlinux.tga}}.}}

====Menu colors====

====Menu colors====

−

As in Grub (0.9x), you can change the menu colors in Grub2. The available colors for GRUB2 are at http://www.gnu.org/software/grub/manual/html_node/Theme-file-format.html#Theme-file-format .

+

You can set the menu colors in GRUB2. The available colors for GRUB2 can be found in [https://www.gnu.org/software/grub/manual/html_node/Theme-file-format.html the GRUB Manual].

Here is an example:

Here is an example:

−

Edit {{Filename|/etc/default/grub}}:

+

Edit {{ic|/etc/default/grub}}:

GRUB_COLOR_NORMAL="light-blue/black"

GRUB_COLOR_NORMAL="light-blue/black"

GRUB_COLOR_HIGHLIGHT="light-cyan/blue"

GRUB_COLOR_HIGHLIGHT="light-cyan/blue"

Line 440:

Line 698:

====Hidden menu====

====Hidden menu====

−

One of the unique features of Grub2 is hiding/skipping the menu and showing it by holding "Shift" when needed. You can also adjust whether you want to see the timeout counter.

+

One of the unique features of GRUB2 is hiding/skipping the menu and showing it by holding {{keypress|Esc}} when needed. You can also adjust whether you want to see the timeout counter.

−

Edit {{Filename|/etc/default/grub}} as you wish. Here is an example where the comments from the beginning of the two lines have been removed to enable the feature, the timeout has been set to five seconds and to be shown to the user:

+

Edit {{ic|/etc/default/grub}} as you wish. Here is an example where the comments from the beginning of the two lines have been removed to enable the feature, the timeout has been set to five seconds and to be shown to the user:

GRUB_HIDDEN_TIMEOUT=5

GRUB_HIDDEN_TIMEOUT=5

GRUB_HIDDEN_TIMEOUT_QUIET=false

GRUB_HIDDEN_TIMEOUT_QUIET=false

and run:

and run:

−

grub-mkconfig -o /boot/grub/grub.cfg

+

# grub-mkconfig -o /boot/grub/grub.cfg

−

====Setting the framebuffer resolution ====

+

====Disable framebuffer====

−

Grub2 can set the framebuffer for both grub2 itself and the kernel. The old ''vga='' way is deprecated. The preferred method is editing {{Filename|/etc/default/grub}} as the following sample:

+

Users who use NVIDIA proprietary driver might wish to disable GRUB2's framebuffer as it can cause problems with the binary driver.

−

GRUB_GFXMODE=1024x768x32

+

To disable framebuffer, edit {{ic|/etc/default/grub}} and uncomment the following line:

−

GRUB_GFXPAYLOAD_LINUX=keep

+

GRUB_TERMINAL_OUTPUT=console

−

To generate the changes, run:

+

and run:

grub-mkconfig -o /boot/grub/grub.cfg

grub-mkconfig -o /boot/grub/grub.cfg

−

−

The {{Codeline|gfxpayload}} property will make sure the kernel keeps the resolution.

−

−

If this method does not work for you, the deprecated <code>vga=</code> method will still work. Just

−

add it next to the <code>"GRUB_CMDLINE_LINUX_DEFAULT="</code> line in {{Filename|/etc/default/grub}}

−

for eg: <code>"GRUB_CMDLINE_LINUX_DEFAULT="quiet splash vga=792"</code> will give you a {{Codeline|1024x768}} resolution.

−

−

You can choose one of these resolutions: {{Codeline|640×480}}, {{Codeline|800×600}}, {{Codeline|1024×768}}, {{Codeline|1280×1024}}, {{Codeline|1600×1200}}

=== Other Options ===

=== Other Options ===

Line 471:

Line 721:

==== LVM ====

==== LVM ====

−

If you use [[LVM]] for your {{Filename|/boot}}, add the following before menuentry lines:

+

If you use [[LVM]] for your {{ic|/boot}}, add the following before menuentry lines:

insmod lvm

insmod lvm

Line 477:

Line 727:

and specify your root in the menuentry as:

and specify your root in the menuentry as:

−

set root=(''lvm_group_name''-''lvm_logical_boot_partition_name'')

+

set root=lvm/''lvm_group_name''-''lvm_logical_boot_partition_name''

Example:

Example:

Line 484:

Line 734:

menuentry "Arch Linux" {

menuentry "Arch Linux" {

insmod lvm

insmod lvm

−

set root=(VolumeGroup-lv_boot)

+

set root=lvm/VolumeGroup-lv_boot

# you can only set following two lines

# you can only set following two lines

linux /vmlinuz-linux root=/dev/mapper/VolumeGroup-root ro

linux /vmlinuz-linux root=/dev/mapper/VolumeGroup-root ro

Line 490:

Line 740:

}

}

−

==== Raid ====

+

==== RAID ====

−

−

Grub2 provides convenient handling of raid-volumes. You need to add:

−

insmod raid

−

which allows you to address the volume natively. E.g. {{Filename|/dev/md0}} becomes:

+

GRUB2 provides convenient handling of RAID volumes. You need to add {{ic|insmod mdraid}} which allows you to address the volume natively. For example, {{ic|/dev/md0}} becomes:

You can use UUIDs to detect partitions instead of the "old" {{Filename|/dev/sd*}} and {{Filename|/dev/hd*}} scheming. It has the advantage of detecting partitions by their unique UUIDs, which is needed by some people booting with complicated partition setups.

+

One naming scheme for [[Persistent block device naming]] is the use of globally unique UUIDs to detect partitions instead of the "old" {{ic|/dev/sd*}}. Advantages are covered up in the above linked article.

+

+

Persistent naming via filesystem UUIDs are used by default in GRUB2.

+

+

{{Note|The {{ic|/boot/grub.cfg}} file needs regeneration with the new UUID in {{ic|/etc/default/grub}} every time a relevant filesystem is resized or recreated. Remember this when modifying partitions & filesystems with a Live-CD.}}

−

UUIDs are used by default in the recent versions of grub2 - there is no downside in it anyway except that you need to re-generate the {{Filename|grub.cfg}} file every time you resize or reformat your partitions. Remember this when modifying partitions with Live-CD.

+

Whether to use UUIDs is controlled by an option in /etc/default/grub:

−

The recent versions of grub2 use UUIDs by default. You can re-enable the use of UUIDS by simply commenting the UUID line (this is also what it looks like by default):

+

{{bc|1=# GRUB_DISABLE_LINUX_UUID=true}}

−

#GRUB_DISABLE_LINUX_UUID=true

−

you can also just set the value as {{Codeline|false}} as shown here:

−

GRUB_DISABLE_LINUX_UUID=false

Either way, do not forget to generate the changes:

Either way, do not forget to generate the changes:

−

grub-mkconfig -o /boot/grub/grub.cfg

+

{{bc|# grub-mkconfig -o /boot/grub/grub.cfg}}

==== Using Labels ====

==== Using Labels ====

−

It is possible to use labels, human-readable strings attached to filesystems, by using the {{Codeline|--label}} option to {{Codeline|search}}. First of all, label your existing partition:

+

It is possible to use labels, human-readable strings attached to filesystems, by using the {{ic|--label}} option to {{ic|search}}. First of all, label your existing partition:

−

# tune2fs -L a <LABEL> <PARTITION>

+

# tune2fs -L <LABEL> <PARTITION>

Then, add an entry using labels. An example of this:

Then, add an entry using labels. An example of this:

menuentry "Arch Linux, session texte" {

menuentry "Arch Linux, session texte" {

−

search --label --no-floppy --set=root archroot

+

search --label --set=root archroot

linux /boot/vmlinuz-linux root=/dev/disk/by-label/archroot ro

linux /boot/vmlinuz-linux root=/dev/disk/by-label/archroot ro

initrd /boot/initramfs-linux.img

initrd /boot/initramfs-linux.img

Line 529:

Line 777:

==== Recall previous entry ====

==== Recall previous entry ====

−

Grub2 can remember the last entry you booted from and use this as the default entry to boot from next time. This is useful if you have multiple kernels (i.e., the current Arch one and the LTS kernel as a fallback option) or operating systems. To do this, edit {{Filename|/etc/default/grub}} and change the setting of {{Codeline|GRUB_DEFAULT}}:

+

GRUB2 can remember the last entry you booted from and use this as the default entry to boot from next time. This is useful if you have multiple kernels (i.e., the current Arch one and the LTS kernel as a fallback option) or operating systems. To do this, edit {{ic|/etc/default/grub}} and change the setting of {{ic|GRUB_DEFAULT}}:

GRUB_DEFAULT=saved

GRUB_DEFAULT=saved

−

This ensures that grub will default to the saved entry. To enable saving the selected entry, add the following line to {{Filename|/etc/default/grub}}:

+

This ensures that GRUB will default to the saved entry. To enable saving the selected entry, add the following line to {{ic|/etc/default/grub}}:

If you want to secure GRUB2 so it is not possible for anyone to change boot parameters or use the command line, you can add a user/password combination to GRUB2's configuration files. To do this, run the command {{Codeline|grub-mkpasswd_pbkdf2}}. Enter a password and confirm it. The output will look like this:

+

If you want to secure GRUB2 so it is not possible for anyone to change boot parameters or use the command line, you can add a user/password combination to GRUB2's configuration files. To do this, run the command {{ic|grub-mkpasswd-pbkdf2}}. Enter a password and confirm it. The output will look like this:

−

<!-- How do I wrap the output of grub-mkpasswd_pdkdf2 into the box? -->

+

{{bc|<nowiki>

−

<pre>Your PBKDF2 is grub.pbkdf2.sha512.10000.C8ABD3E93C4DFC83138B0C7A3D719BC650E6234310DA069E6FDB0DD4156313DA3D0D9BFFC2846C21D5A2DDA515114CF6378F8A064C94198D0618E70D23717E82.509BFA8A4217EAD0B33C87432524C0B6B64B34FBAD22D3E6E6874D9B101996C5F98AB1746FE7C7199147ECF4ABD8661C222EEEDB7D14A843261FFF2C07B1269A</pre>Then, add the following to {{Filename|/etc/grub.d/00_header}}:

+

Your PBKDF2 is grub.pbkdf2.sha512.10000.C8ABD3E93C4DFC83138B0C7A3D719BC650E6234310DA069E6FDB0DD4156313DA3D0D9BFFC2846C21D5A2DDA515114CF6378F8A064C94198D0618E70D23717E82.509BFA8A4217EAD0B33C87432524C0B6B64B34FBAD22D3E6E6874D9B101996C5F98AB1746FE7C7199147ECF4ABD8661C222EEEDB7D14A843261FFF2C07B1269A</nowiki>}}Then, add the following to {{ic|/etc/grub.d/00_header}}:

−

<pre>cat << EOF

+

{{bc|<nowiki>cat << EOF

set superusers="username"

set superusers="username"

password_pbkdf2 username <password>

password_pbkdf2 username <password>

−

EOF</pre>

+

EOF</nowiki>}}

−

where <password> is the string generated by {{Codeline|grub-mkpasswd_pbkdf2}}.

+

where {{ic|<password>}} is the string generated by {{ic|grub-mkpasswd_pbkdf2}}.

add {{ic|1=cryptdevice=/dev/yourdevice:label}} to {{ic|GRUB_CMDLINE_LINUX}} in {{ic|/etc/default/grub}}.

+

+

Example with root mapped to {{ic|/dev/mapper/root}}:

+

+

GRUB_CMDLINE_LINUX="cryptdevice=/dev/sda2:root"

+

+

Also, disable the usage of UUIDs for the rootfs:

+

+

GRUB_DISABLE_LINUX_UUID=true

+

+

Regenerate the configuration.

+

+

==== Boot non-default entry only once ====

+

+

The command {{ic|grub-reboot}} is very helpful to boot another entry than the default only once. GRUB2 loads the entry passed in the first command line argument, when the system is rebooted the next time. Most importantly GRUB2 returns to loading the default entry for all future booting. Changing the configuration file or selecting an entry in the GRUB2 menu is not necessary.

+

+

=== Booting an ISO Directly From GRUB2 ===

+

Edit {{ic|/etc/grub.d/40_custom}} or {{ic|/boot/grub/custom.cfg}} to add an entry for the target ISO. When finished, update the GRUB menu as with the usual {{ic|grub-mkconfig -o /boot/grub/grub.cfg}} (as root).

+

+

==== Arch ISO ====

+

{{Note|The example assumes that the iso is in {{ic|/archives}} on {{ic|hd0,6}}. Users must adjust the location and hdd/partition in ALL of the lines below to match their systems. However, if booting the ISO from USB on a computer which also has one internal HDD, then it needs to be {{ic|hd0,Y}} with {{ic|sdbY}}, instead of {{ic|sdaY}}.}}

Other working configurations from [http://askubuntu.com/questions/141940/how-to-boot-live-iso-images link Source].

== Using the command shell ==

== Using the command shell ==

−

Since the MBR is too small to store all GRUB2 modules, only the menu and a few basic commands reside there. The majority of GRUB2 functionality remains in modules in {{Filename|/boot/grub}}, which are inserted as needed. In error conditions (e.g. if the partition layout changes) GRUB2 may fail to boot. When this happens, a command shell may appear.

+

Since the MBR is too small to store all GRUB2 modules, only the menu and a few basic commands reside there. The majority of GRUB2 functionality remains in modules in {{ic|/boot/grub}}, which are inserted as needed. In error conditions (e.g. if the partition layout changes) GRUB2 may fail to boot. When this happens, a command shell may appear.

GRUB2 offers multiple shells/prompts. If there is a problem reading the menu but the bootloader is able to find the disk, you will likely be dropped to the "normal" shell:

GRUB2 offers multiple shells/prompts. If there is a problem reading the menu but the bootloader is able to find the disk, you will likely be dropped to the "normal" shell:

Line 567:

Line 874:

The rescue shell is a restricted subset of the normal shell, offering much less functionality. If dumped to the rescue shell, first try inserting the "normal" module, then starting the "normal" shell:

The rescue shell is a restricted subset of the normal shell, offering much less functionality. If dumped to the rescue shell, first try inserting the "normal" module, then starting the "normal" shell:

*:GUI app for changing the settings of GRUB, GRUB2, Usplash and Splashy

*:GUI app for changing the settings of GRUB, GRUB2, Usplash and Splashy

−

== parttool or legacy hide/unhide ==

+

== parttool for hide/unhide ==

−

If you have a win9x paradigm with hidden C disks GRUB legacy had the hide/unhide feature. In GRUB2 this has been replaced by parttool. For example, to boot the third C disk of three win9x installations on the CLI enter the CLI and:

+

If you have a Windows 9x paradigm with hidden C:\ disks GRUB can hide/unhide it using {{ic|parttool}}. For example, to boot the third C:\ disk of three Windows 9x installations on the CLI enter the CLI and:

parttool hd0,1 hidden+ boot-

parttool hd0,1 hidden+ boot-

parttool hd0,2 hidden+ boot-

parttool hd0,2 hidden+ boot-

Line 599:

Line 908:

See [[#Using the command shell]] first. If unable to activate the standard shell, one possible solution is to boot using a live CD or some other rescue disk to correct configuration errors and reinstall GRUB. However, such a boot disk is not always available (nor necessary); the rescue console is surprisingly robust.

See [[#Using the command shell]] first. If unable to activate the standard shell, one possible solution is to boot using a live CD or some other rescue disk to correct configuration errors and reinstall GRUB. However, such a boot disk is not always available (nor necessary); the rescue console is surprisingly robust.

−

The available commands in GRUB rescue include "insmod", "ls", "set", and "unset". This example uses "set" and "insmod". "set" modifies variables and "insmod" inserts new modules to add functionality.

+

The available commands in GRUB rescue include {{ic|insmod}}, {{ic|ls}}, {{ic|set}}, and {{ic|unset}}. This example uses {{ic|set}} and {{ic|insmod}}. {{ic|set}} modifies variables and {{ic|insmod}} inserts new modules to add functionality.

−

Before starting, the user must know the location of their {{Filename|/boot}} partition (be it a separate partition, or a subdirectory under their root):

+

Before starting, the user must know the location of their {{ic|/boot}} partition (be it a separate partition, or a subdirectory under their root):

This introduces the "linux" and "initrd" commands, which should be familiar (see [[#Configuration]]).

+

This introduces the {{ic|linux}} and {{ic|initrd}} commands, which should be familiar (see [[#Configuration]]).

An example, booting Arch Linux:

An example, booting Arch Linux:

Line 625:

Line 934:

boot

boot

−

After successfully booting the Arch Linux installation, users can correct {{Filename|grub.cfg}} as needed and then run:

+

After successfully booting the Arch Linux installation, users can correct {{ic|grub.cfg}} as needed and then reinstall GRUB2.

−

# grub-install /dev/sda --no-floppy

−

to reinstall GRUB2 and fix the problem completely, changing {{Filename|/dev/sda}} if needed. See [[#Bootloader installation]] for details.

+

to reinstall GRUB2 and fix the problem completely, changing {{ic|/dev/sda}} if needed. See [[#Bootloader installation]] for details.

−

== Combining the use of UUID's and basic scripting ==

+

== Combining the use of UUIDs and basic scripting ==

−

If you like the idea of using UUID's to avoid unreliable BIOS mappings or are struggling with Grub's syntax, here is an example boot menu item that uses UUID's and a small script to direct Grub to the proper disk partitions for your system. All you need to do is replace the UUID's in the sample with the correct UUID's for your system. (The example applies to a system with a boot and root partition. You will obviously need to modify the Grub configuration if you have additional partitions.)

+

If you like the idea of using UUIDs to avoid unreliable BIOS mappings or are struggling with GRUB's syntax, here is an example boot menu item that uses UUIDs and a small script to direct GRUB to the proper disk partitions for your system. All you need to do is replace the UUIDs in the sample with the correct UUIDs for your system. The example applies to a system with a boot and root partition. You will obviously need to modify the GRUB configuration if you have additional partitions:

menuentry "Arch Linux 64" {

menuentry "Arch Linux 64" {

−

#Enter the UUID of your boot partition (this is where Grub and your kernel reside)

+

# Set the UUIDs for your boot and root partition respectively

−

set uuid_grub_boot=ece0448f-bb08-486d-9864-ac3271bd8d07

+

set the_boot_uuid=ece0448f-bb08-486d-9864-ac3271bd8d07

−

+

set the_root_uuid=c55da16f-e2af-4603-9e0b-03f5f565ec4a

−

#Enter the UUID of the partition containing the root partition of your Arch Linux installation.

−

set uuid_os_root=c55da16f-e2af-4603-9e0b-03f5f565ec4a

−

−

#(Note: this may be the same as your boot partition)

−

#Here we set the Grub "root" variable by locating the UUID of the root partition identified above

+

# (Note: This may be the same as your boot partition)

−

search --fs-uuid --no-floppy --set=root $uuid_os_root

−

#Here we set a custom variable grub_boot by locating the UUID of the boot partition identified above

+

# Get the boot/root devices and set them in the root and grub_boot variables

−

search --fs-uuid --no-floppy --set=grub_boot $uuid_grub_boot

+

search --fs-uuid --set=root $the_root_uuid

+

search --fs-uuid --set=grub_boot $the_boot_uuid

−

#Here is the magic. We test to see if the boot and root partitions have the same UUID.

+

# Check to see if boot and root are equal.

−

#If they do, we append /boot to the $grub_boot variable. For ex. (hd0,1) becomes (hd0,1)/boot.

+

# If they are, then append /boot to $grub_boot (Since $grub_boot is actually the root partition)

−

if [ $uuid_grub_boot == $uuid_os_root ] ; then

+

if [ $the_boot_uuid == $the_root_uuid] ; then

−

set grub_boot=$grub_boot/boot

+

set grub_boot=$grub_boot/boot

−

fi

+

fi

−

# $grub_boot now points to the correct location, so the following will properly find the kernel and initrd

+

# $grub_boot now points to the correct location, so the following will properly find the kernel and initrd

Then you need to initialize GRUB2 graphical terminal ({{ic|gfxterm}}) with proper video mode ({{ic|gfxmode}}) in GRUB2. This video mode is passed by GRUB2 to the linux kernel via 'gfxpayload'. In case of UEFI systems, if the GRUB2 video mode is not initialized, no kernel boot messages will be shown in the terminal (atleast until KMS kicks in).

+

+

Copy {{ic|/usr/share/grub/unicode.pf2}} to ${GRUB2_PREFIX_DIR} ({{ic|/boot/grub/}} in case of BIOS and UEFI systems). If GRUB2 UEFI was installed with {{ic|1=--boot-directory=/boot/efi/EFI}} set, then the directory is {{ic|/boot/efi/EFI/grub/}}:

+

+

# cp /usr/share/grub/unicode.pf2 ${GRUB2_PREFIX_DIR}

+

+

If {{ic|/usr/share/grub/unicode.pf2}} does not exist, install {{Pkg|bdf-unifont}}, create the {{ic|unifont.pf2}} file and then copy it to {{ic|${GRUB2_PREFIX_DIR<nowiki>}</nowiki>}}:

+

+

# grub-mkfont -o unicode.pf2 /usr/share/fonts/misc/unifont.bdf

+

+

Then, in the {{ic|grub.cfg}} file, add the following lines to enable GRUB2 to pass the video mode correctly to the kernel, without of which you will only get a black screen (no output) but booting (actually) proceeds successfully without any system hang.

+

+

BIOS systems:

+

+

insmod vbe

+

+

UEFI systems:

+

+

insmod efi_gop

+

insmod efi_uga

+

+

After that add the following code (common to both BIOS and UEFI):

+

+

insmod font

+

+

if loadfont ${prefix}/fonts/unicode.pf2

+

then

+

insmod gfxterm

+

set gfxmode=auto

+

set gfxpayload=keep

+

terminal_output gfxterm

+

fi

+

+

As you can see for gfxterm (graphical terminal) to function properly, {{ic|unicode.pf2}} font file should exist in {{ic|${GRUB2_PREFIX_DIR<nowiki>}</nowiki>}}.

=== msdos-style error message ===

=== msdos-style error message ===

Line 671:

Line 1,026:

grub-setup: error: If you really want blocklists, use --force.

grub-setup: error: If you really want blocklists, use --force.

−

This error may occur when you try installing GRUB2 in a VMware container. Read more about it [http://bbs.archlinux.org/viewtopic.php?pid=581760#p581760 here]. Hopefully a fix will be provided soon.

+

This error may occur when you try installing GRUB2 in a VMware container. Read more about it [https://bbs.archlinux.org/viewtopic.php?pid=581760#p581760 here]. It happens when the first partition starts just after the MBR (block 63), without the usual space of 1 MiB (2048 blocks) before the first partition. Read [[#Master Boot Record (MBR) specific instructions]]

+

+

=== UEFI GRUB2 drops to shell ===

−

It also happens when the first partition starts just after the MBR (block 63), without the usual space of 1MB (2048 blocks) before the first partition.

+

If GRUB loads but drops you into the rescue shell with no errors, it may be because of a missing or misplaced {{ic|grub.cfg}}. This will happen if GRUB2 UEFI was installed with {{ic|--boot-directory}} and {{ic|grub.cfg}} is missing OR if the partition number of the boot partition changed (which is hard-coded into the {{ic|grubx64.efi}} file).

−

=== Grub not loaded ===

+

=== UEFI GRUB2 not loaded ===

−

In some cases the EFI may fail to load grub correctly. Provided everything is set up correctly, the output of

+

In some cases the EFI may fail to load GRUB correctly. Provided everything is set up correctly, the output of:

If everything works correctly, the EFI would now automatically load grub.<br>

+

If everything works correctly, the EFI would now automatically load GRUB.

−

If the screen only goes black for a second and the next boot option is tried afterwards, according to [https://bbs.archlinux.org/viewtopic.php?pid=981560#p981560 this post], moving grub to the partition root can help. The boot option has to be deleted and recreated afterwards. The entry for grub should look like this then:

+

+

If the screen only goes black for a second and the next boot option is tried afterwards, according to [https://bbs.archlinux.org/viewtopic.php?pid=981560#p981560 this post], moving GRUB to the partition root can help. The boot option has to be deleted and recreated afterwards. The entry for GRUB should look like this then:

In brief, the bootloader is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the Linux kernel. The kernel, in turn, initializes the rest of the operating system.

Notes for current GRUB Legacy users

Upgrade from GRUB Legacy to GRUB2 is the much same as fresh installing GRUB2 which is covered below.

There are differences in the commands of GRUB and GRUB2. Familiarize yourself with GRUB2 commands before proceeding (e.g. "find" has been replaced with "search").

GRUB2 is now modular and no longer requires "stage 1.5". As a result, the bootloader itself is limited -- modules are loaded from the hard drive as needed to expand functionality (e.g. for LVM or RAID support).

Device naming has changed between GRUB and GRUB2. Partitions are numbered from 1 instead of 0 while drives are still numbered from 0, and prefixed with partition-table type. For example, /dev/sda1 would be referred to as (hd0,msdos1) (for MBR) or (hd0,gpt1) (for GPT) using GRUB2.

Preliminary Requirements for GRUB2

BIOS systems

GRUB2 in BIOS-GPT configuration requires a BIOS Boot Partition to embed its core.img in the absence of post-MBR gap in GPT partitioned systems (which is taken over by the GPT Primary Header and Primary Partition table). This partition is used by GRUB2 only in BIOS-GPT setups. No such partition type exists in case of MBR partitioning (at least not for GRUB2). This partition is also not required if the system is UEFI based, as no embedding of bootsectors takes place in that case. Syslinux does not require this partition.

For a BIOS-GPT configuration, create a 1007 KiB partition at the beginning of the disk using cgdisk or GNU Parted with no filesystem. The size of 1007 KiB will allow for the following partition to be correctly alligned at 1024 KiB. If needed, the partition can also be located somewhere else on the disk, but it should be within the first 2 TiB region. Set the partition type to 0xEF02 in gdisk, EF02 in cgdisk or set <BOOT_PART_NUM> bios_grub on in GNU Parted.

Note: This partition should be created before grub-install or grub-setup is run.

Note: gdisk will only allow you to create this partition on the position which will waste the least amount of space (sector 34-2047) if you create it last, after all the other partitions. This is because gdisk will auto-align partitions to 2048-sector boundaries if possible.

Usually the post-MBR gap (after the 512 byte MBR region and before the start of the 1st partition) in many MBR (or msdos disklabel) partitioned systems is 31 KiB when DOS compatibility cylinder alignment issues are satisfied in the partition table. However a post-MBR gap of about 1 to 2 MiB is recommended to provide sufficient room for embedding GRUB2's core.img (FS#24103). It is advisable to use a partitioner which supports 1 MiB partition alignment to obtain this space as well as satisfy other non-512 byte sector issues (which are unrelated to embedding of core.img).

MBR partitioning has better support in other operating systems, such as Microsoft Windows (up to Windows 7) and Haiku, than GPT partitioning. If you dual boot another operating system, consider using MBR partitioning.

UEFI systems

Create and Mount the UEFI System Partition

Follow Unified Extensible Firmware Interface#EFI System Partition for instructions on creating a UEFI SYSTEM PARTITION. Then mount the UEFI SYSTEM PARTITION at /boot/efi. If you have mounted the UEFISYS partition in some other mountpoint, replace /boot/efi in the below instructions with that mountpoint:

# mkdir -p /boot/efi
# mount -t vfat <UEFISYS_PART_DEVICE> /boot/efi

Create a <UEFI_SYSTEM_PARTITION>/EFI directory, if it does not exist:

# mkdir -p /boot/efi/EFI

Installation

BIOS systems

Backup Important Data

Although a GRUB(2) installation should run smoothly, it is strongly recommended to keep the GRUB Legacy files before installing grub-bios.

Only 446 bytes of the MBR contain boot code, the next 64 contain the partition table. If you do not want to overwrite your partition table when restoring, it is strongly advised to backup only the MBR boot code:

Install grub-bios package

The GRUB(2) packages can be installed with pacman (and will replace grub-legacy or grub, if it is installed):

# pacman -S grub-bios

Note: Simply installing the package won't update the /boot/grub/i386-pc/core.img file and the GRUB(2) modules in /boot/grub/i386-pc. You need to update them manually using grub-install as explained below.

where /dev/sda is the destination of the installation (in this case the MBR of the first SATA disk). If you use LVM for your /boot, you can install GRUB2 on multiple physical disks.

Note: --no-floppy has been removed from grub-install in 2.00~beta2 upstream release, and replaced with --allow-floppy.

Warning: Make sure to check the /boot directory if you use the latter. Sometimes the boot-directory parameter creates another /boot folder inside of /boot. A wrong install would look like: /boot/boot/grub/.

Install to GPT BIOS Boot Partition

GUID Partition Table disks do not have a reserved "boot track". Therefore you must create a BIOS Boot Partition (0xEF02) to hold the GRUB core image.

Using GNU Parted, you can set this using a command such as the following:

# parted /dev/disk set <partition-number> bios_grub on

If you are using gdisk, set the partition type to Template:Keypress. With partitioning programs that require setting the GUID directly, it should be ‘21686148-6449-6e6f-744e656564454649’ (stored on disk as "Hah!IdontNeedEFI" if interpreted as ASCII).

Warning: Be very careful which partition you select when marking it as a BIOS Boot Partition. When GRUB finds a BIOS Boot Partition during installation, it will automatically overwrite part of it. Make sure that the partition does not contain any other data.

To setup grub-bios on a GPT disk, populate the /boot/grub directory, generate the /boot/grub/i386-pc/core.img file, and embed it in the BIOS Boot Partition, run:

Install to Partition or Partitionless Disk

Note: grub-bios (any version - including upstream Bazaar repo) does not encourage installation to a partition boot sector or a partitionless disk like GRUB Legacy or Syslinux does. This kind of setup is prone to breakage, especially during updates, and is not supported by Arch devs.

To set up grub-bios to a partition boot sector, to a partitionless disk (also called superfloppy) or to a floppy disk, run (using for example /dev/sdaX as the /boot partition):

You need to use the --force option to allow usage of blocklists and should not use --grub-setup=/bin/true (which is similar to simply generating core.img).

grub-install will give out warnings like which should give you the idea of what might go wrong with this approach:

/sbin/grub-setup: warn: Attempting to install GRUB to a partitionless disk or to a partition. This is a BAD idea.
/sbin/grub-setup: warn: Embedding is not possible. GRUB can only be installed in this setup by using blocklists.
However, blocklists are UNRELIABLE and their use is discouraged.

Without --force you may get the below error and grub-setup will not setup its boot code in the partition boot sector:

/sbin/grub-setup: error: will not proceed with blocklists

With --force you should get:

Installation finished. No error reported.

The reason why grub-setup does not by default allow this is because in case of partition or a partitionless disk is that grub-bios relies on embedded blocklists in the partition bootsector to locate the /boot/grub/i386-pc/core.img file and the prefix dir /boot/grub. The sector locations of core.img may change whenever the filesystem in the partition is being altered (files copied, deleted etc.). For more info see https://bugzilla.redhat.com/show_bug.cgi?id=728742 and https://bugzilla.redhat.com/show_bug.cgi?id=730915.

The workaround for this is to set the immutable flag on /boot/grub/i386-pc/core.img (using chattr command as mentioned above) so that the sector locations of the core.img file in the disk is not altered. The immutable flag on /boot/grub/i386-pc/core.img needs to be set only if grub-bios is installed to a partition boot sector or a partitionless disk, not in case of installation to MBR or simple generation of core.img without embedding any bootsector (mentioned above).

Generate core.img alone

To populate the /boot/grub directory and generate a /boot/grub/i386-pc/core.img file without embedding any grub-bios bootsector code in the MBR, post-MBR region, or the partition bootsector, add --grub-setup=/bin/true to grub-install:

Multiboot in BIOS

Boot Microsoft Windows installed in BIOS-MBR mode

Note: GRUB(2) supports booting bootmgr directly and chainload of partition boot sector is no longer required to boot Windows in a BIOS-MBR setup.

Warning: Take note that it is the system partition that has bootmgr, not your "real" Windows partition (usually C:). When showing all UUIDs with blkid, the system partition is the one with LABEL="SYSTEM RESERVED" and is only about 100 MB in size (much like the boot partition for Arch). See http://en.wikipedia.org/wiki/System_partition_and_boot_partition for more info.

Find the UUID of the NTFS filesystem of the Windows's SYSTEM PARTITION where the bootmgr and its files reside. For example, if Windows bootmgr exists at /media/SYSTEM_RESERVED/bootmgr:

/etc/grub.d/40_custom can be used as a template to create /etc/grub.d/nn_custom. Where nn defines the precendence, indicating the order the script is executed. The order scripts are executed determine the placement in the grub boot menu.

Note: nn should be greater than 06 to ensure necessary scripts are executed first.

UEFI systems

Hardware-Specific UEFI Examples

It is well know that different motherboard manufactures implement UEFI differently. Users experiencing problems getting Grub/EFI to work properly are encouraged to share detailed steps for hardware-specific cases where UEFI booting does not work as described below. In an effort to keep the parent GRUB article neat and tidy, see the GRUB EFI Examples page for these special cases.

Install grub-uefi package

Note: Unless specified as EFI 1.x , EFI and UEFI terms are used interchangeably to denote UEFI 2.x firmware. Also unless stated explicitly, the instructions are general and not Mac specific. Some of them may not work or may be different in Macs. Apple's EFI implementation is neither a EFI 1.x version nor UEFI 2.x version but mixes up both. This kind of firmware does not fall under any one UEFI Specification version and is therefore not a standard UEFI firmware.

GRUB(2) UEFI bootloader is available in Arch Linux only from version 1.99~rc1. To install, first detect which UEFI firmware arch you have (either x86_64 or i386).

Depending on that, install the appropriate package

For 64-bit aka x86_64 UEFI firmware:

# pacman -S grub-efi-x86_64

For 32-bit aka i386 UEFI firmware:

# pacman -S grub-efi-i386

Note: Simply installing the package will not update the core.efi file and the GRUB(2) modules in the UEFI System Partition. You need to do this manually using grub-install as explained below.

Install grub-uefi boot files

Install to UEFI System Partition

Note: The below commands assume you are using grub-efi-x86_64 (for grub-efi-i386 replace x86_64 with i386 in the below commands).

Note: To do this, you need to boot using UEFI and not the BIOS. If you booted by just copying the ISO file to the USB drive, you will need to follow this guide or grub-install will show errors.

The UEFI system partition will need to be mounted at /boot/efi/ for the GRUB(2) install script to detect it:

# mkdir -p /boot/efi
# mount -t vfat /dev/sdXY /boot/efi

Install GRUB UEFI application to /boot/efi/EFI/arch_grub and its modules to /boot/grub/x86_64-efi (recommended) using:

Note: Without --target or --directory option, grub-install cannot determine for which firmware grub(2) is being installed. In such cases grub-install will show source_dir doesn't exist. Please specify --target or --directory message.

If you want to install grub(2) modules and grub.cfg at the directory /boot/efi/EFI/grub and the grubx64.efi application at /boot/efi/EFI/arch_grub (ie. all the grub(2) uefi files inside the UEFISYS partition itself) use:

The --efi-directory option mentions the mountpoint of UEFI SYSTEM PARTITION , --bootloader-id mentions the name of the directory used to store the grubx64.efi file and --boot-directory mentions the directory wherein the actual modules will be installed (and into which grub.cfg should be created).

The <efi-directory>/<EFI or efi>/<bootloader-id>/grubx64.efi is an exact copy of <boot-directory>/grub/x86_64-efi/core.efi.

Note: In GRUB 2.00, the grub-install option --efi-directory replaces --root-directory and the latter is deprecated.

Note: The options --efi-directory and --bootloader-id are specific to GRUB(2) UEFI.

In all the cases the UEFI SYSTEM PARTITION should be mounted for grub-install to install grubx64.efi in it, which will be launched by the firmware (using the efibootmgr created boot entry in non-Mac systems).

If you notice carefully, there is no <device_path> option (Eg: /dev/sda) at the end of the grub-install command unlike the case of setting up GRUB(2) for BIOS systems. Any <device_path> provided will be ignored by the install script as UEFI bootloaders do not use MBR or Partition boot sectors at all.

Create GRUB2 Standalone UEFI Application

It is possible to create a grubx64_standalone.efi application which has all the modules embeddded in a memdisk within the uefi application, thus removing the need for having a separate directory populated with all the GRUB2 uefi modules and other related files. This is done using the grub-mkstandalone command which is included in grub-common >= 1:1.99-6 package.

The easiest way to do this would be with the install command already mentioned before, but specifying the modules to include. For example:

The grubx64_standalone.efi file expects grub.cfg to be within its $prefix which is (memdisk)/boot/grub. The memdisk is embedded within the efi app. The grub-mkstandlone script allow passing files to be included in the memdisk image to be as the arguments to the script (in <any extra files you want to include>).

If you have the grub.cfg at /home/user/Desktop/grub.cfg, then create a temporary /home/user/Desktop/boot/grub/ directory, copy the /home/user/Desktop/grub.cfg to /home/user/Desktop/boot/grub/grub.cfg, cd into /home/user/Desktop/boot/grub/ and run:

The reason to cd into /home/user/Desktop/boot/grub/ and to pass the file path as boot/grub/grub.cfg (notice the lack of a leading slash - boot/ vs /boot/ ) is because dir1/dir2/file is included as (memdisk)/dir1/dir2/file by the grub-mkstandalone script.

If you pass /home/user/Desktop/grub.cfg the file will be included as (memdisk)/home/user/Desktop/grub.cfg. If you pass /home/user/Desktop/boot/grub/grub.cfg the file will be included as (memdisk)/home/user/Desktop/boot/grub/grub.cfg. That is the reason for cd'ing into /home/user/Desktop/boot/grub/ and passing boot/grub/grub.cfg, to include the file as (memdisk)/boot/grub/grub.cfg, which is what grub.efi expects the file to be.

Multiboot in UEFI

Chainload Microsoft Windows x86_64 UEFI-GPT

Find the UUID of the FAT32 filesystem in the UEFI SYSTEM PARTITION where the Windows UEFI Bootloader files reside. For example, if Windows bootmgfw.efi exists at /boot/efi/EFI/Microsoft/Boot/bootmgfw.efi (ignore the upper-lower case differences since that is immaterial in FAT filesystem):

Configuration

You can also choose to automatically generate or manually edit grub.cfg.

Note: For EFI systems, if GRUB2 was installed with the --boot-directory option set, the grub.cfg file must be placed in the same directory as grubx64.efi. Otherwise, the grub.cfg file goes in /boot/grub/, just like in the BIOS version of GRUB2.

Automatically generating using grub-mkconfig (Recommended)

The GRUB2 menu.lst equivalent configuration files are /etc/default/grub and /etc/grub.d/*. grub-mkconfig uses these files to generate grub.cfg. By default the script outputs to stdout. To generate a grub.cfg file run the command:

# grub-mkconfig -o /boot/grub/grub.cfg

/etc/grub.d/10_linux is set to automatically add menu items for Arch linux that work out of the box, to any generated configuration. Other operating systems may need to be added manually to /etc/grub.d/40_custom or /boot/grub/custom.cfg

Additional arguments

To pass custom additional arguments to the Linux image, you can set the GRUB_CMDLINE_LINUX variable in /etc/default/grub.

For example, use GRUB_CMDLINE_LINUX="resume=/dev/sdaX" where sdaX is your swap partition to enable resume after hibernation.

You can also use GRUB_CMDLINE_LINUX="resume=/dev/disk/by-uuid/${swap_uuid}", where ${swap_uuid} is the UUID of your swap partition.

Multiple entries are separated by spaces within the double quotes. So, for users who want both resume and systemd it would look like this:
GRUB_CMDLINE_LINUX="resume=/dev/sdaX init=/usr/lib/systemd/systemd"

Manually creating grub.cfg

Warning: Editing this file is strongly not recommended. The file is generated by the grub-mkconfig command, and it is best to edit your /etc/default/grub or one of the scripts in the /etc/grub.d folder.

Dual-booting

Note: If you want GRUB2 to automatically search for other systems, you may wish to install os-prober.

Using grub-mkconfig

The best way to add other entries is editing the /etc/grub.d/40_custom or /boot/grub/custom.cfg . The entries in this file will be automatically added when running grub-mkconfig.
After adding the new lines, run:

With FreeBSD

Requires that FreeBSD is installed on a single partition with UFS. Assuming it is installed on sda4:

menuentry "FreeBSD" {
set root=(hd0,4)
chainloader +1
}

With Windows

This assumes that your Windows partition is sda3. Remember you need to point set root and chainloader to the system reserve partition that windows made when it installed, not the actual partition windows is on. This example works if your system reserve partition is sda3.

If the Windows bootloader is on an entirely different hard drive than GRUB, it may be necessary to trick Windows into believing that it is the first hard drive. This was possible with drivemap. Assuming GRUB is on hd0 and Windows is on hd2, you need to add the following after set root:

drivemap -s hd0 hd2

With Windows via EasyBCD and NeoGRUB

Since EasyBCD's NeoGRUB currently does not understand the GRUB2 menu format, chainload to it by replacing the contents of your C:\NST\menu.lst file with lines similar to the following:

Visual Configuration

In GRUB2 it is possible, by default, to change the look of the menu. Make sure to initialize, if not done already, GRUB2 graphical terminal, gfxterm, with proper video mode, gfxmode, in GRUB2. This can be seen in the section #Correct_GRUB2_No_Suitable_Mode_Found_Error. This video mode is passed by GRUB2 to the linux kernel via 'gfxpayload' so any visual configurations need this mode in order to be in effect.

Setting the framebuffer resolution

GRUB2 can set the framebuffer for both GRUB2 itself and the kernel. The old vga= way is deprecated. The preferred method is editing /etc/default/grub as the following sample:

GRUB_GFXMODE=1024x768x32
GRUB_GFXPAYLOAD_LINUX=keep

To generate the changes, run:

# grub-mkconfig -o /boot/grub/grub.cfg

The gfxpayload property will make sure the kernel keeps the resolution.

Note: If this example does not work for you try to replace gfxmode="1024x768x32" by vbemode="0x105". Remember to replace the specified resolution with one suitable for your screen.

Note: To show all the modes you can use # hwinfo --framebuffer (hwinfo is available in [community]), while at GRUB2 prompt you can use the vbeinfo command.

If this method does not work for you, the deprecated vga= method will still work. Just
add it next to the "GRUB_CMDLINE_LINUX_DEFAULT=" line in /etc/default/grub
for eg: "GRUB_CMDLINE_LINUX_DEFAULT="quiet splash vga=792" will give you a 1024x768 resolution.

You can choose one of these resolutions: 640×480, 800×600, 1024×768, 1280×1024, 1600×1200, 1920×1200

915resolution hack

Some times for Intel graphic adapters neither # hwinfo --framebuffer nor vbeinfo will show you the desired resolution. In this case you can use 915resolution hack. This hack will temporarily modify video BIOS and add needed resolution. See 915resolution's home page

In the following I will proceed with the example for my system. Please adjust the recipe for your needs. First you need to find a video mode which will be modified later. For that, run 915resolution in GRUB2 command shell:

Next, our purpose is to overwrite mode 30. (You can choose what ever mode you want.) In the file /etc/grub.d/00_header just before the set gfxmode=${GRUB_GFXMODE} line insert:

915resolution 30 1440 900

Here we are overwriting the mode 30 with 1440x900 resolution. Lastly we need to set GRUB_GFXMODE as described earlier, regenerate GRUB2 configuration file and reboot to test changes:

# grub-mkconfig -o /boot/grub/grub.cfg
# reboot

Background image and bitmap fonts

GRUB2 comes with support for background images and bitmap fonts in pf2 format. The unifont font is included in the grub-common package under the filename unicode.pf2, or, as only ASCII characters under the name ascii.pf2.

Note: If you have installed GRUB on a separate partition, /boot/grub/myimage becomes /grub/myimage.

To generate the changes and add the information into grub.cfg, run:

grub-mkconfig -o /boot/grub/grub.cfg

If adding the splash image was successful, the user will see "Found background image..." in the terminal as the command is executed.
If this phrase is not seen, the image information was probably not incorporated into the grub.cfg file.

If the image is not displayed, check:

The path and the filename in /etc/default/grub are correct.

The image is of the proper size and format (tga, png, 8-bit jpg).

The image was saved in the RGB mode, and is not indexed.

The console mode is not enabled in /etc/default/grub.

The command grub-mkconfig must be executed to place the background image information into the /boot/grub/grub.cfg file.

Theme

Here is an example for configuring Starfield theme which was included in GRUB2 package.

Edit /etc/default/grub

GRUB_THEME="/usr/share/grub/themes/starfield/theme.txt"

Generate the changes:

grub-mkconfig -o /boot/grub/grub.cfg

If configuring the theme was successful, you'll see Found theme: /usr/share/grub/themes/starfield/theme.txt in the terminal.
Your splash image will usually not be displayed when using a theme.

Menu colors

You can set the menu colors in GRUB2. The available colors for GRUB2 can be found in the GRUB Manual.
Here is an example:

Hidden menu

One of the unique features of GRUB2 is hiding/skipping the menu and showing it by holding Template:Keypress when needed. You can also adjust whether you want to see the timeout counter.

Edit /etc/default/grub as you wish. Here is an example where the comments from the beginning of the two lines have been removed to enable the feature, the timeout has been set to five seconds and to be shown to the user:

GRUB_HIDDEN_TIMEOUT=5
GRUB_HIDDEN_TIMEOUT_QUIET=false

and run:

# grub-mkconfig -o /boot/grub/grub.cfg

Disable framebuffer

Users who use NVIDIA proprietary driver might wish to disable GRUB2's framebuffer as it can cause problems with the binary driver.

To disable framebuffer, edit /etc/default/grub and uncomment the following line:

GRUB_TERMINAL_OUTPUT=console

and run:

grub-mkconfig -o /boot/grub/grub.cfg

Other Options

LVM

If you use LVM for your /boot, add the following before menuentry lines:

RAID

GRUB2 provides convenient handling of RAID volumes. You need to add insmod mdraid which allows you to address the volume natively. For example, /dev/md0 becomes:

set root=(md0)

whereas a partitioned RAID volume (e.g. /dev/md0p1) becomes:

set root=(md0,1)

Persistent block device naming

One naming scheme for Persistent block device naming is the use of globally unique UUIDs to detect partitions instead of the "old" /dev/sd*. Advantages are covered up in the above linked article.

Persistent naming via filesystem UUIDs are used by default in GRUB2.

Note: The /boot/grub.cfg file needs regeneration with the new UUID in /etc/default/grub every time a relevant filesystem is resized or recreated. Remember this when modifying partitions & filesystems with a Live-CD.

Whether to use UUIDs is controlled by an option in /etc/default/grub:

# GRUB_DISABLE_LINUX_UUID=true

Either way, do not forget to generate the changes:

# grub-mkconfig -o /boot/grub/grub.cfg

Using Labels

It is possible to use labels, human-readable strings attached to filesystems, by using the --label option to search. First of all, label your existing partition:

Recall previous entry

GRUB2 can remember the last entry you booted from and use this as the default entry to boot from next time. This is useful if you have multiple kernels (i.e., the current Arch one and the LTS kernel as a fallback option) or operating systems. To do this, edit /etc/default/grub and change the setting of GRUB_DEFAULT:

GRUB_DEFAULT=saved

This ensures that GRUB will default to the saved entry. To enable saving the selected entry, add the following line to /etc/default/grub:

Security

If you want to secure GRUB2 so it is not possible for anyone to change boot parameters or use the command line, you can add a user/password combination to GRUB2's configuration files. To do this, run the command grub-mkpasswd-pbkdf2. Enter a password and confirm it. The output will look like this:

Boot non-default entry only once

The command grub-reboot is very helpful to boot another entry than the default only once. GRUB2 loads the entry passed in the first command line argument, when the system is rebooted the next time. Most importantly GRUB2 returns to loading the default entry for all future booting. Changing the configuration file or selecting an entry in the GRUB2 menu is not necessary.

Booting an ISO Directly From GRUB2

Edit /etc/grub.d/40_custom or /boot/grub/custom.cfg to add an entry for the target ISO. When finished, update the GRUB menu as with the usual grub-mkconfig -o /boot/grub/grub.cfg (as root).

Arch ISO

Note: The example assumes that the iso is in /archives on hd0,6. Users must adjust the location and hdd/partition in ALL of the lines below to match their systems. However, if booting the ISO from USB on a computer which also has one internal HDD, then it needs to be hd0,Y with sdbY, instead of sdaY.

Other ISOs

Using the command shell

Since the MBR is too small to store all GRUB2 modules, only the menu and a few basic commands reside there. The majority of GRUB2 functionality remains in modules in /boot/grub, which are inserted as needed. In error conditions (e.g. if the partition layout changes) GRUB2 may fail to boot. When this happens, a command shell may appear.

GRUB2 offers multiple shells/prompts. If there is a problem reading the menu but the bootloader is able to find the disk, you will likely be dropped to the "normal" shell:

sh:grub>

If there is a more serious problem (e.g. GRUB cannot find required files), you may instead be dropped to the "rescue" shell:

grub rescue>

The rescue shell is a restricted subset of the normal shell, offering much less functionality. If dumped to the rescue shell, first try inserting the "normal" module, then starting the "normal" shell:

Using the rescue console

See #Using the command shell first. If unable to activate the standard shell, one possible solution is to boot using a live CD or some other rescue disk to correct configuration errors and reinstall GRUB. However, such a boot disk is not always available (nor necessary); the rescue console is surprisingly robust.

The available commands in GRUB rescue include insmod, ls, set, and unset. This example uses set and insmod. set modifies variables and insmod inserts new modules to add functionality.

Before starting, the user must know the location of their /boot partition (be it a separate partition, or a subdirectory under their root):

grub rescue> set prefix=(hdX,Y)/boot/grub

where X is the physical drive number and Y is the partition number.

To expand console capabilities, insert the linux module:

grub rescue> insmod (hdX,Y)/boot/grub/linux.mod

Note: With a separate boot partition, omit /boot from the path, (i.e. type set prefix=(hdX,Y)/grub and insmod (hdX,Y)/grub/linux.mod).

This introduces the linux and initrd commands, which should be familiar (see #Configuration).

After successfully booting the Arch Linux installation, users can correct grub.cfg as needed and then reinstall GRUB2.

to reinstall GRUB2 and fix the problem completely, changing /dev/sda if needed. See #Bootloader installation for details.

Combining the use of UUIDs and basic scripting

If you like the idea of using UUIDs to avoid unreliable BIOS mappings or are struggling with GRUB's syntax, here is an example boot menu item that uses UUIDs and a small script to direct GRUB to the proper disk partitions for your system. All you need to do is replace the UUIDs in the sample with the correct UUIDs for your system. The example applies to a system with a boot and root partition. You will obviously need to modify the GRUB configuration if you have additional partitions:

menuentry "Arch Linux 64" {
# Set the UUIDs for your boot and root partition respectively
set the_boot_uuid=ece0448f-bb08-486d-9864-ac3271bd8d07
set the_root_uuid=c55da16f-e2af-4603-9e0b-03f5f565ec4a
# (Note: This may be the same as your boot partition)
# Get the boot/root devices and set them in the root and grub_boot variables
search --fs-uuid --set=root $the_root_uuid
search --fs-uuid --set=grub_boot $the_boot_uuid
# Check to see if boot and root are equal.
# If they are, then append /boot to $grub_boot (Since $grub_boot is actually the root partition)
if [ $the_boot_uuid == $the_root_uuid] ; then
set grub_boot=$grub_boot/boot
fi
# $grub_boot now points to the correct location, so the following will properly find the kernel and initrd
linux ($grub_boot)/vmlinuz-linux root=/dev/disk/by-uuid/$uuid_os_root ro
initrd ($grub_boot)/initramfs-linux.img
}

Troubleshooting

Any troubleshooting should be added here.

Enable GRUB2 debug messages

Add:

set pager=1
set debug=all

to grub.cfg.

Correct GRUB2 No Suitable Mode Found Error

If you get this error when booting any menuentry:

error: no suitable mode found
Booting however

Then you need to initialize GRUB2 graphical terminal (gfxterm) with proper video mode (gfxmode) in GRUB2. This video mode is passed by GRUB2 to the linux kernel via 'gfxpayload'. In case of UEFI systems, if the GRUB2 video mode is not initialized, no kernel boot messages will be shown in the terminal (atleast until KMS kicks in).

Copy /usr/share/grub/unicode.pf2 to ${GRUB2_PREFIX_DIR} (/boot/grub/ in case of BIOS and UEFI systems). If GRUB2 UEFI was installed with --boot-directory=/boot/efi/EFI set, then the directory is /boot/efi/EFI/grub/:

# cp /usr/share/grub/unicode.pf2 ${GRUB2_PREFIX_DIR}

If /usr/share/grub/unicode.pf2 does not exist, install bdf-unifont, create the unifont.pf2 file and then copy it to ${GRUB2_PREFIX_DIR}:

# grub-mkfont -o unicode.pf2 /usr/share/fonts/misc/unifont.bdf

Then, in the grub.cfg file, add the following lines to enable GRUB2 to pass the video mode correctly to the kernel, without of which you will only get a black screen (no output) but booting (actually) proceeds successfully without any system hang.

BIOS systems:

insmod vbe

UEFI systems:

insmod efi_gop
insmod efi_uga

After that add the following code (common to both BIOS and UEFI):

insmod font

if loadfont ${prefix}/fonts/unicode.pf2
then
insmod gfxterm
set gfxmode=auto
set gfxpayload=keep
terminal_output gfxterm
fi

As you can see for gfxterm (graphical terminal) to function properly, unicode.pf2 font file should exist in ${GRUB2_PREFIX_DIR}.

msdos-style error message

grub-setup: warn: This msdos-style partition label has no post-MBR gap; embedding won't be possible!
grub-setup: warn: Embedding is not possible. GRUB can only be installed in this setup by using blocklists.
However, blocklists are UNRELIABLE and its use is discouraged.
grub-setup: error: If you really want blocklists, use --force.

This error may occur when you try installing GRUB2 in a VMware container. Read more about it here. It happens when the first partition starts just after the MBR (block 63), without the usual space of 1 MiB (2048 blocks) before the first partition. Read #Master Boot Record (MBR) specific instructions

UEFI GRUB2 drops to shell

If GRUB loads but drops you into the rescue shell with no errors, it may be because of a missing or misplaced grub.cfg. This will happen if GRUB2 UEFI was installed with --boot-directory and grub.cfg is missing OR if the partition number of the boot partition changed (which is hard-coded into the grubx64.efi file).

UEFI GRUB2 not loaded

In some cases the EFI may fail to load GRUB correctly. Provided everything is set up correctly, the output of:

If everything works correctly, the EFI would now automatically load GRUB.

If the screen only goes black for a second and the next boot option is tried afterwards, according to this post, moving GRUB to the partition root can help. The boot option has to be deleted and recreated afterwards. The entry for GRUB should look like this then: